I had improved in Term 3 as compared to Term 1 and 2. I learnt many things like the kinetic particle theory, forces, weight,density, mass, scientists' tools, flames and measurement. I also learnt how to draw a graph and also a straight line graph. In practical, we did experiments on flames, measurement of length and time, density of object, elements, compound and mixtures, separation techniques, inside cell and photosynthesis and respiration carried out by plants.
I find that the practical lessons made me like science as it is very fun and I can test theories with with my friends. I hope that I can continue to do more experiments to have more interest in science. To improve my grades, I can revise my work more and practice more.
Sunday, September 26, 2010
Difference between Mass and Weight
Mass is defined as the amount of matter an object has. However, the weight of an object on earth depends on the force of attraction (gravity) between the object and earth. In one of the more common definitions, the weight of an object, often denoted by W, is defined as being equal to the force exerted on it by gravity. This force is the product of the mass m of the object and the local gravitational acceleration g. Expressed in a formula: W = mg
An equipment used to measure the mass of an object is the scale or the beam balance.
An equipment used to measure the weight of an object is the spring balance or the compression balance.
The mass of object is constant everywhere while he weight of an object changes from place to place.
The SI unit for mass is kilogram while the SI unit for weight is Newton.
An equipment used to measure the mass of an object is the scale or the beam balance.
An equipment used to measure the weight of an object is the spring balance or the compression balance.
The mass of object is constant everywhere while he weight of an object changes from place to place.
The SI unit for mass is kilogram while the SI unit for weight is Newton.
Thursday, September 9, 2010
Forming compounds
My friends and I did an experiment to investigate the formation of compounds by reacting two elements, reacting an element and a compound and reacting two compounds. The experiment needs magnesium ribbon, iron filings, dilute sulfuric acid, lead (II) nitrate solution, sodium chloride, test –tube, Bunsen burner, evaporating dish, test-tube holder and a pair of tongs.
Reacting two elements
1. Hold a magnesium ribbon with a pair of tongs. Place it in the Bunsen flame. When the magnesium ribbon catches fire, hold the pair of tongs above the evaporating dish to collect the ashes formed. The magnesium ribbon burned with a bright white light.
2. The ash is white in colour.
3. A new substance has formed because the physical appearance has changed from silvery grey to white in colour and heat is also involved in this reaction.
4. Oxygen has combined with magnesium to form a compound.
5. Magnesium + oxygen = magnesium oxide
Reacting an element with a compound
1. Place half a spatula of iron filings in a test-tube.
2. Add dilute sulfuric acid to a depth of about 2 cm. Effervescence of colourless, odourless gas is seen.
3. A new substance has formed because the test-tube felt warm indicating that heat has been released and the colour of the substance also changed to light grey.
4. Iron + Sulfuric acid = iron sulfate + hydrogen gas
Reacting two compounds
1. Place sodium chloride solution in a test-tube to a depth of about 2 cm.
2. Using a dropper, add lead (II) nitrate solution slowly to the test-tube. White precipitate can be seen.
3. Sodium chloride + lead (II) nitrate = sodium nitrate + lead (II) chloride
Metals have high boiling and melting point where as non-metals have low boiling and melting point. Metals form oxides that are basic while non-metal form oxides that are acidic. Metals are solid at room temperature while non-metal are solids, liquids or gases at room temperature.
Reacting two elements
1. Hold a magnesium ribbon with a pair of tongs. Place it in the Bunsen flame. When the magnesium ribbon catches fire, hold the pair of tongs above the evaporating dish to collect the ashes formed. The magnesium ribbon burned with a bright white light.
2. The ash is white in colour.
3. A new substance has formed because the physical appearance has changed from silvery grey to white in colour and heat is also involved in this reaction.
4. Oxygen has combined with magnesium to form a compound.
5. Magnesium + oxygen = magnesium oxide
Reacting an element with a compound
1. Place half a spatula of iron filings in a test-tube.
2. Add dilute sulfuric acid to a depth of about 2 cm. Effervescence of colourless, odourless gas is seen.
3. A new substance has formed because the test-tube felt warm indicating that heat has been released and the colour of the substance also changed to light grey.
4. Iron + Sulfuric acid = iron sulfate + hydrogen gas
Reacting two compounds
1. Place sodium chloride solution in a test-tube to a depth of about 2 cm.
2. Using a dropper, add lead (II) nitrate solution slowly to the test-tube. White precipitate can be seen.
3. Sodium chloride + lead (II) nitrate = sodium nitrate + lead (II) chloride
Metals have high boiling and melting point where as non-metals have low boiling and melting point. Metals form oxides that are basic while non-metal form oxides that are acidic. Metals are solid at room temperature while non-metal are solids, liquids or gases at room temperature.
Wednesday, September 8, 2010
Investigating mixtures and compounds
My friends and I did some experiments to investigate the properties of a mixture and a compound. The experiment needs tripod stand, evaporating dish, glass rod, wire gauze, Bunsen burner, sulfur powder, iron filings, filter paper and a magnet wrapped in a small piece of paper.
Both sulfur and iron are elements. When they are mixed, a mixture of iron and sulfur is formed and when they are heated together, a compound, iron sulfide is formed.
Observing Elements
1. Place the sulfur powder on a piece of filter paper. The sulfur is in a form of yellow powder.
2. Wrap on end of the magnet with a small piece of paper the move the magnet close to the sulfur powder. The sulfur powder is not being attracted by the magnet.
3. Place the iron filings in an evaporating dish. The iron filings are in a form of black powder.
4. Move the magnet close to the iron filings. The iron filings are being attracted to the magnet.
Observing a mixture
5. Pour the sulfur powder into the evaporating dish of iron filings. Mix it thoroughly with the iron filings using a glass rod. The mixture is a mixture of yellow and black powder.
6. Move the magnet close to the mixture. Only the iron filings are being attracted to the magnet.
Observing a compound
7. Heat the evaporating dish over the Bunsen flame until no more change occurs. Allow the evaporating dish to cool. The compound is in a form of a dark grey powder.
8. Move the magnet close to the compound. The compound is not attracted to the magnet.
I think that the mixture of iron and sulfur has the properties of iron and sulfur because no heat is released or taken in and the basic appearances of black and yellow powder are still evident.
Heat is needed for a compound to form.
I think that the compound formed from iron and sulfur does not have the properties of iron and sulfur because the colour is entirely different from its constituent components and no parts of the compound is attracted to the magnet.
Hence, I can conclude that heat is not needed to form a mixture but heat is needed to form a compound. A mixture has the properties of its constituent elements while a compound does not have the properties of its constituent elements. A mixture can be separated into its elements by physical methods but a compound cannot be separated into its elements by physical methods.
Both sulfur and iron are elements. When they are mixed, a mixture of iron and sulfur is formed and when they are heated together, a compound, iron sulfide is formed.
Observing Elements
1. Place the sulfur powder on a piece of filter paper. The sulfur is in a form of yellow powder.
2. Wrap on end of the magnet with a small piece of paper the move the magnet close to the sulfur powder. The sulfur powder is not being attracted by the magnet.
3. Place the iron filings in an evaporating dish. The iron filings are in a form of black powder.
4. Move the magnet close to the iron filings. The iron filings are being attracted to the magnet.
Observing a mixture
5. Pour the sulfur powder into the evaporating dish of iron filings. Mix it thoroughly with the iron filings using a glass rod. The mixture is a mixture of yellow and black powder.
6. Move the magnet close to the mixture. Only the iron filings are being attracted to the magnet.
Observing a compound
7. Heat the evaporating dish over the Bunsen flame until no more change occurs. Allow the evaporating dish to cool. The compound is in a form of a dark grey powder.
8. Move the magnet close to the compound. The compound is not attracted to the magnet.
I think that the mixture of iron and sulfur has the properties of iron and sulfur because no heat is released or taken in and the basic appearances of black and yellow powder are still evident.
Heat is needed for a compound to form.
I think that the compound formed from iron and sulfur does not have the properties of iron and sulfur because the colour is entirely different from its constituent components and no parts of the compound is attracted to the magnet.
Hence, I can conclude that heat is not needed to form a mixture but heat is needed to form a compound. A mixture has the properties of its constituent elements while a compound does not have the properties of its constituent elements. A mixture can be separated into its elements by physical methods but a compound cannot be separated into its elements by physical methods.
Testing for the presence of starch
My friends and I did an experiment to test if there are starch on a variegated leaf. The experiment needs boiling water, beaker, ethanol, boiling tube, glass rod, white tile and iodine solution.
1. Place the leaf in the dark for sometime so the leaf will not photosynthesize
2. Take the leaf and put in the beaker and fill the beaker with boiling water
3. Leave the leaf in boiling water for a while to kill it
4. Take the leaf out and put it in the boiling tube then fill it with ethanol
5. Use the glass rod and stir the ethanol until the leaf changes colour (the use of the ethanol is to remove the chlorophyll in the leaf)
6. Take the leaf out and then rinse it in water
7. Place the leaf on the white tile and drop some iodine solution on the leaf
After a while, the iodine solution on the green pigment of the leaf turned blue black while the iodine solution on the non green part of the leaf remained yellowish brown. Hence, I can conclude that chlorophyll is needed for photosynthesis as there is no chlorophyll in the non green part of the variegated leaf.
1. Place the leaf in the dark for sometime so the leaf will not photosynthesize
2. Take the leaf and put in the beaker and fill the beaker with boiling water
3. Leave the leaf in boiling water for a while to kill it
4. Take the leaf out and put it in the boiling tube then fill it with ethanol
5. Use the glass rod and stir the ethanol until the leaf changes colour (the use of the ethanol is to remove the chlorophyll in the leaf)
6. Take the leaf out and then rinse it in water
7. Place the leaf on the white tile and drop some iodine solution on the leaf
After a while, the iodine solution on the green pigment of the leaf turned blue black while the iodine solution on the non green part of the leaf remained yellowish brown. Hence, I can conclude that chlorophyll is needed for photosynthesis as there is no chlorophyll in the non green part of the variegated leaf.
Sunday, September 5, 2010
Newton's laws of motion
Newton's laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. They have been expressed in several different ways over nearly three centuries, and can be summarised as follows:
1. First Law: Every body remains in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force. This means that in the absence of a non-zero net force, the center of mass of a body either remains at rest, or moves at a constant speed in a straight line.
2. Second Law: A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body.
3. Third Law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the "action" and −F the "reaction".
The laws of motion were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton used them to explain and investigate the motion of many physical objects and systems. For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion.
Newton's laws are applied to bodies (objects) which are considered or idealized as a particle, in the sense that the extent of the body is neglected in the evaluation of its motion, i.e., the object is small compared to the distances involved in the analysis, or the deformation and rotation of the body is of no importance in the analysis. Therefore, a planet can be idealized as a particle for analysis of its orbital motion around a star.
The first law states that if the resultant force (the vector sum of all forces acting on an object) is zero, then the velocity of the object is constant. Consequently:
• An object that is at rest will stay at rest unless an unbalanced force acts upon it.
• An object that is in motion will not change its velocity unless an unbalanced force acts upon it.
Newton's laws are valid only in an inertial reference frame. Any reference frame that is in uniform motion with respect to an inertial frame is also an inertial frame, i.e. Galilean invariance or the principle of Newtonian relativity.
Newton's first law is a restatement of the law of inertia which Galileo had already described and Newton gave credit to Galileo. Aristotle had the view that all objects have a natural place in the universe: that heavy objects like rocks wanted to be at rest on the Earth and that light objects like smoke wanted to be at rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed to continually propel it, otherwise it would stop moving. Galileo, however, realized that a force is necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. This insight leads to Newton's First Law —no force means no acceleration, and hence the body will maintain its velocity.
The second law states that F=ma. Thus, the net force applied to a body produces a proportional acceleration. Any mass that is gained or lost by the system will cause a change in momentum that is not the result of an external force. A different equation is necessary for variable-mass systems. Consistent with the first law, the time derivative of the momentum is non-zero when the momentum changes direction, even if there is no change in its magnitude; such is the case with uniform circular motion. The relationship also implies the conservation of momentum: when the net force on the body is zero, the momentum of the body is constant. Any net force is equal to the rate of change of the momentum. Newton's second law requires modification if the effects of special relativity are to be taken into account, because at high speeds the approximation that momentum is the product of rest mass and velocity is not accurate.
The Third Law means that all forces are interactions between different bodies, and thus that there is no such thing as a unidirectional force or a force that acts on only one body. If body A exerts a force on body B, body B simultaneously exerts a force of the same magnitude on body A— both forces acting along the same line. An example is two skaters, the skaters' forces on each other are equal in magnitude, but act in opposite directions. Although the forces are equal, the accelerations are not: the less massive skater will have a greater acceleration due to Newton's second law. The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force on an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires pushing backward on the road).
Newton used the third law to derive the law of conservation of momentum; however from a deeper perspective, conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics.
In my opinion, I feel that Newton is very capable as he was the first to discover the laws of motion. These laws are very beneficial to us as it would enable us to understand things we have observed in greater depth and it serves as a stepping stone to scientists who would like to find out more about the motion of an object in detailed.
1. First Law: Every body remains in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force. This means that in the absence of a non-zero net force, the center of mass of a body either remains at rest, or moves at a constant speed in a straight line.
2. Second Law: A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body.
3. Third Law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the "action" and −F the "reaction".
The laws of motion were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton used them to explain and investigate the motion of many physical objects and systems. For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion.
Newton's laws are applied to bodies (objects) which are considered or idealized as a particle, in the sense that the extent of the body is neglected in the evaluation of its motion, i.e., the object is small compared to the distances involved in the analysis, or the deformation and rotation of the body is of no importance in the analysis. Therefore, a planet can be idealized as a particle for analysis of its orbital motion around a star.
The first law states that if the resultant force (the vector sum of all forces acting on an object) is zero, then the velocity of the object is constant. Consequently:
• An object that is at rest will stay at rest unless an unbalanced force acts upon it.
• An object that is in motion will not change its velocity unless an unbalanced force acts upon it.
Newton's laws are valid only in an inertial reference frame. Any reference frame that is in uniform motion with respect to an inertial frame is also an inertial frame, i.e. Galilean invariance or the principle of Newtonian relativity.
Newton's first law is a restatement of the law of inertia which Galileo had already described and Newton gave credit to Galileo. Aristotle had the view that all objects have a natural place in the universe: that heavy objects like rocks wanted to be at rest on the Earth and that light objects like smoke wanted to be at rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed to continually propel it, otherwise it would stop moving. Galileo, however, realized that a force is necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. This insight leads to Newton's First Law —no force means no acceleration, and hence the body will maintain its velocity.
The second law states that F=ma. Thus, the net force applied to a body produces a proportional acceleration. Any mass that is gained or lost by the system will cause a change in momentum that is not the result of an external force. A different equation is necessary for variable-mass systems. Consistent with the first law, the time derivative of the momentum is non-zero when the momentum changes direction, even if there is no change in its magnitude; such is the case with uniform circular motion. The relationship also implies the conservation of momentum: when the net force on the body is zero, the momentum of the body is constant. Any net force is equal to the rate of change of the momentum. Newton's second law requires modification if the effects of special relativity are to be taken into account, because at high speeds the approximation that momentum is the product of rest mass and velocity is not accurate.
The Third Law means that all forces are interactions between different bodies, and thus that there is no such thing as a unidirectional force or a force that acts on only one body. If body A exerts a force on body B, body B simultaneously exerts a force of the same magnitude on body A— both forces acting along the same line. An example is two skaters, the skaters' forces on each other are equal in magnitude, but act in opposite directions. Although the forces are equal, the accelerations are not: the less massive skater will have a greater acceleration due to Newton's second law. The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force on an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires pushing backward on the road).
Newton used the third law to derive the law of conservation of momentum; however from a deeper perspective, conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics.
In my opinion, I feel that Newton is very capable as he was the first to discover the laws of motion. These laws are very beneficial to us as it would enable us to understand things we have observed in greater depth and it serves as a stepping stone to scientists who would like to find out more about the motion of an object in detailed.
Friday, September 3, 2010
Maglev
Maglev, or magnetic levitation, is a system of transportation that suspends, guides and propels vehicles, predominantly trains, using magnetic levitation from a very large number of magnets for lift and propulsion. This method has the potential to be faster, quieter and smoother than wheeled mass transit systems. The power needed for levitation is usually not a particularly large percentage of the overall consumption; most of the power used is needed to overcome air drag, as with any other high speed train.
The highest recorded speed of a Maglev train is 581 kilometres per hour (361 mph), achieved in Japan in 2003, 6 kilometres per hour (3.7 mph) faster than the conventional TGV speed record.
The first commercial Maglev "people-mover" was officially opened in 1984 in Birmingham, England. It operated on an elevated 600-metre (2,000 ft) section of monorail track between Birmingham International Airport and Birmingham International railway station, running at speeds up to 42 km/h (26 mph); the system was eventually closed in 1995 due to reliability and design problems.
Perhaps the most well known implementation of high-speed maglev technology currently operating commercially is the IOS (initial operating segment) demonstration line of the German-built Transrapid train in Shanghai, China that transports people 30 km (18.6 miles) to the airport in just 7 minutes 20 seconds, achieving a top speed of 431 km/h (268 mph), averaging 250 km/h (160 mph).
First patents
High speed transportation patents were granted to various inventors throughout the world. Early United States patents for a linear motor propelled train were awarded to the inventor, Alfred Zehden (German). The inventor was awarded U.S. Patent 782,312 (June 21, 1902) and U.S. Patent RE12,700 (August 21, 1907). In 1907, another early electromagnetic transportation system was developed by F. S. Smith. A series of German patents for magnetic levitation trains propelled by linear motors were awarded to Hermann Kemper between 1937 and 1941. An early modern type of maglev train was described in U.S. Patent 3,158,765, Magnetic system of transportation, by G. R. Polgreen (August 25, 1959). The first use of "maglev" in a United States patent was in "Magnetic levitation guidance" by Canadian Patents and Development Limited
Technology Overview
The term "maglev" refers not only to the vehicles, but to the railway system as well, specifically designed for magnetic levitation and propulsion. All operational implementations of maglev technology have had minimal overlap with wheeled train technology and have not been compatible with conventional rail tracks. Because they cannot share existing infrastructure, these maglev systems must be designed as complete transportation systems. The Applied Levitation SPM Maglev system is inter-operable with steel rail tracks and would permit maglev vehicles and conventional trains to operate at the same time on the same right of way. MAN in Germany also designed a maglev system that worked with conventional rails, but it was never fully developed.
There are two particularly notable types of maglev technology:
• For electromagnetic suspension (EMS), electromagnets in the train attract it to a magnetically conductive (usually steel) track.
• Electrodynamic suspension (EDS) uses electromagnets on both track and train to push the train away from the rail.
Another experimental technology, which was designed, proven mathematically, peer reviewed, and patented, but is yet to be built, is the magnetodynamic suspension (MDS), which uses the attractive magnetic force of a permanent magnet array near a steel track to lift the train and hold it in place. Other technologies such as repulsive permanent magnets and superconducting magnets have seen some research.
Advantages and disadvantages
Compared to conventional trains
Major comparative differences between the two technologies lie in backward-compatibility, rolling resistance, weight, noise, design constraints, and control systems.
• Backwards Compatibility: Maglev trains currently in operation are not compatible with conventional track, and therefore require all new infrastructure for their entire route. By contrast conventional high speed trains such as the TGV are able to run at reduced speeds on existing rail infrastructure, thus reducing expenditure where new infrastructure would be particularly expensive (such as the final approaches to city terminals), or on extensions where traffic does not justify new infrastructure.
• Efficiency: Due to the lack of physical contact between the track and the vehicle, maglev trains experience no rolling resistance, leaving only air resistance and electromagnetic drag, potentially improving power efficiency.
• Weight: The weight of the large electromagnets in many EMS and EDS designs is a major design issue. A very strong magnetic field is required to levitate a massive train. For this reason one research path is using superconductors to improve the efficiency of the electromagnets, and the energy cost of maintaining the field.
• Noise: Because the major source of noise of a maglev train comes from displaced air, maglev trains produce less noise than a conventional train at equivalent speeds. However, the psychoacoustic profile of the maglev may reduce this benefit: a study concluded that maglev noise should be rated like road traffic while conventional trains have a 5-10 dB "bonus" as they are found less annoying at the same loudness level.
• Design Comparisons: Braking and overhead wire wear have caused problems for the Fastech 360 railed Shinkansen. Maglev would eliminate these issues. Magnet reliability at higher temperatures is a countervailing comparative disadvantage (see suspension types), but new alloys and manufacturing techniques have resulted in magnets that maintain their levitational force at higher temperatures.
As with many technologies, advances in linear motor design have addressed the limitations noted in early maglev systems. As linear motors must fit within or straddle their track over the full length of the train, track design for some EDS and EMS maglev systems is challenging for anything other than point-to-point services. Curves must be gentle, while switches are very long and need care to avoid breaks in current. An SPM maglev system, in which the vehicle is permanently levitated over the tracks, can instantaneously switch tracks using electronic controls, with no moving parts in the track. A prototype SPM maglev train has also navigated curves with radius equal to the length of the train itself, which indicates that a full-scale train should be able to navigate curves with the same or narrower radius as a conventional train.
• Control Systems: EMS Maglev needs very fast-responding control systems to maintain a stable height above the track; this needs careful design in the event of a failure in order to avoid crashing into the track during a power fluctuation. Other maglev systems do not necessarily have this problem. For example, SPM maglev systems have a stable levitation gap of several centimeters.
A Maglev train has it advantages and disadvantages. Hence you cannot say which train, whether the Maglev train or the conventional train is the best but I think that it should depend on the person riding it whether which train is more suitable for himself.
The highest recorded speed of a Maglev train is 581 kilometres per hour (361 mph), achieved in Japan in 2003, 6 kilometres per hour (3.7 mph) faster than the conventional TGV speed record.
The first commercial Maglev "people-mover" was officially opened in 1984 in Birmingham, England. It operated on an elevated 600-metre (2,000 ft) section of monorail track between Birmingham International Airport and Birmingham International railway station, running at speeds up to 42 km/h (26 mph); the system was eventually closed in 1995 due to reliability and design problems.
Perhaps the most well known implementation of high-speed maglev technology currently operating commercially is the IOS (initial operating segment) demonstration line of the German-built Transrapid train in Shanghai, China that transports people 30 km (18.6 miles) to the airport in just 7 minutes 20 seconds, achieving a top speed of 431 km/h (268 mph), averaging 250 km/h (160 mph).
First patents
High speed transportation patents were granted to various inventors throughout the world. Early United States patents for a linear motor propelled train were awarded to the inventor, Alfred Zehden (German). The inventor was awarded U.S. Patent 782,312 (June 21, 1902) and U.S. Patent RE12,700 (August 21, 1907). In 1907, another early electromagnetic transportation system was developed by F. S. Smith. A series of German patents for magnetic levitation trains propelled by linear motors were awarded to Hermann Kemper between 1937 and 1941. An early modern type of maglev train was described in U.S. Patent 3,158,765, Magnetic system of transportation, by G. R. Polgreen (August 25, 1959). The first use of "maglev" in a United States patent was in "Magnetic levitation guidance" by Canadian Patents and Development Limited
Technology Overview
The term "maglev" refers not only to the vehicles, but to the railway system as well, specifically designed for magnetic levitation and propulsion. All operational implementations of maglev technology have had minimal overlap with wheeled train technology and have not been compatible with conventional rail tracks. Because they cannot share existing infrastructure, these maglev systems must be designed as complete transportation systems. The Applied Levitation SPM Maglev system is inter-operable with steel rail tracks and would permit maglev vehicles and conventional trains to operate at the same time on the same right of way. MAN in Germany also designed a maglev system that worked with conventional rails, but it was never fully developed.
There are two particularly notable types of maglev technology:
• For electromagnetic suspension (EMS), electromagnets in the train attract it to a magnetically conductive (usually steel) track.
• Electrodynamic suspension (EDS) uses electromagnets on both track and train to push the train away from the rail.
Another experimental technology, which was designed, proven mathematically, peer reviewed, and patented, but is yet to be built, is the magnetodynamic suspension (MDS), which uses the attractive magnetic force of a permanent magnet array near a steel track to lift the train and hold it in place. Other technologies such as repulsive permanent magnets and superconducting magnets have seen some research.
Advantages and disadvantages
Compared to conventional trains
Major comparative differences between the two technologies lie in backward-compatibility, rolling resistance, weight, noise, design constraints, and control systems.
• Backwards Compatibility: Maglev trains currently in operation are not compatible with conventional track, and therefore require all new infrastructure for their entire route. By contrast conventional high speed trains such as the TGV are able to run at reduced speeds on existing rail infrastructure, thus reducing expenditure where new infrastructure would be particularly expensive (such as the final approaches to city terminals), or on extensions where traffic does not justify new infrastructure.
• Efficiency: Due to the lack of physical contact between the track and the vehicle, maglev trains experience no rolling resistance, leaving only air resistance and electromagnetic drag, potentially improving power efficiency.
• Weight: The weight of the large electromagnets in many EMS and EDS designs is a major design issue. A very strong magnetic field is required to levitate a massive train. For this reason one research path is using superconductors to improve the efficiency of the electromagnets, and the energy cost of maintaining the field.
• Noise: Because the major source of noise of a maglev train comes from displaced air, maglev trains produce less noise than a conventional train at equivalent speeds. However, the psychoacoustic profile of the maglev may reduce this benefit: a study concluded that maglev noise should be rated like road traffic while conventional trains have a 5-10 dB "bonus" as they are found less annoying at the same loudness level.
• Design Comparisons: Braking and overhead wire wear have caused problems for the Fastech 360 railed Shinkansen. Maglev would eliminate these issues. Magnet reliability at higher temperatures is a countervailing comparative disadvantage (see suspension types), but new alloys and manufacturing techniques have resulted in magnets that maintain their levitational force at higher temperatures.
As with many technologies, advances in linear motor design have addressed the limitations noted in early maglev systems. As linear motors must fit within or straddle their track over the full length of the train, track design for some EDS and EMS maglev systems is challenging for anything other than point-to-point services. Curves must be gentle, while switches are very long and need care to avoid breaks in current. An SPM maglev system, in which the vehicle is permanently levitated over the tracks, can instantaneously switch tracks using electronic controls, with no moving parts in the track. A prototype SPM maglev train has also navigated curves with radius equal to the length of the train itself, which indicates that a full-scale train should be able to navigate curves with the same or narrower radius as a conventional train.
• Control Systems: EMS Maglev needs very fast-responding control systems to maintain a stable height above the track; this needs careful design in the event of a failure in order to avoid crashing into the track during a power fluctuation. Other maglev systems do not necessarily have this problem. For example, SPM maglev systems have a stable levitation gap of several centimeters.
A Maglev train has it advantages and disadvantages. Hence you cannot say which train, whether the Maglev train or the conventional train is the best but I think that it should depend on the person riding it whether which train is more suitable for himself.
Mpemba effect
The Mpemba effect is the observation that, in certain specific circumstances, warmer water freezes faster than colder water. New Scientist recommends starting the experiment with containers at 35 °C (95 °F) and 5 °C (41 °F) to maximize the effect.
Origin
The effect is named for the Tanzanian high-school student Erasto Mpemba. Mpemba first encountered the phenomenon in 1963 in Form 3 of Magamba Secondary School, Tanzania when freezing hot ice cream mix in cookery classes and noticing that they froze before cold mixes. After passing his O-level examinations, he became a student at Mkwawa Secondary (formerly High) School, Iringa, Tanzania. The headmaster invited Dr. Denis G. Osborne from the University College in Dar Es Salaam to give a lecture on physics. After the lecture, Erasto Mpemba asked him the question "If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?" only to be ridiculed by his classmates and teacher. After initial consternation, Dr. Osborne experimented on the issue back at his workplace and confirmed Erasto's finding. They published the results together in 1969.
Causes
Osborne observed that the top is warmer than the bottom in a beaker of water being cooled, the difference being sustained by convection. Blocking heat transfer from the top with a film of oil drastically slowed cooling. Also, the effect of dissolved air was accounted for by using boiled water. The beakers were also insulated from the bottom.
At first sight, the behaviour seems contrary to thermodynamics. Many standard physical theory effects contribute to the phenomenon, although no single explanation is conclusive. Several effects may contribute to the observation, depending on the experimental set-up:
• Definition of frozen: Is it the physical definition of the point at which water forms a visible surface layer of ice, or the point at which the entire volume of water becomes a solid block of ice? Some experiments have instead measured the time until the water reached 0°C.
• Evaporation: Reducing the volume to be frozen. Evaporation is endothermic, but this alone probably does not account for the entirety of the effect.
• Convection: Accelerating heat transfers. Reduction of water density below 4 °C (39 °F) tends to suppress the convection currents that cool the lower part of the liquid mass; the lower density of hot water would reduce this effect, perhaps sustaining the more rapid initial cooling. Higher convection in the warmer water may also spread ice crystals around faster.
• Frost: Has insulating effects. The lower temperature water will tend to freeze from the top, reducing further heat loss by radiation and air convection, while the warmer water will tend to freeze from the bottom and sides because of water convection. This is disputed as there are experiments that account for this factor.
• Supercooling: It is hypothesized that cold water, when placed in a freezing environment, supercools more than hot water in the same environment, thus solidifying slower than hot water. However, supercooling tends to be less significant where there are particles that act as nuclei for ice crystals, thus precipitating rapid freezing.
• Solutes: The effects of calcium, magnesium carbonate among others.
• The effect of heating on dissolved gases; however, this was accounted for in the original article by using boiled water.
It is very amazing to me as I cannot imagine hot water freezing faster than cold water. It seems almost impossible. Mpemba is curious and hence he managed to discover this theory. He is also very brave as he raised a question which other people thinks is ridiculous. So, to be an accomplished scientist, we must have a curious mind and is willing to learn more.
Origin
The effect is named for the Tanzanian high-school student Erasto Mpemba. Mpemba first encountered the phenomenon in 1963 in Form 3 of Magamba Secondary School, Tanzania when freezing hot ice cream mix in cookery classes and noticing that they froze before cold mixes. After passing his O-level examinations, he became a student at Mkwawa Secondary (formerly High) School, Iringa, Tanzania. The headmaster invited Dr. Denis G. Osborne from the University College in Dar Es Salaam to give a lecture on physics. After the lecture, Erasto Mpemba asked him the question "If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?" only to be ridiculed by his classmates and teacher. After initial consternation, Dr. Osborne experimented on the issue back at his workplace and confirmed Erasto's finding. They published the results together in 1969.
Causes
Osborne observed that the top is warmer than the bottom in a beaker of water being cooled, the difference being sustained by convection. Blocking heat transfer from the top with a film of oil drastically slowed cooling. Also, the effect of dissolved air was accounted for by using boiled water. The beakers were also insulated from the bottom.
At first sight, the behaviour seems contrary to thermodynamics. Many standard physical theory effects contribute to the phenomenon, although no single explanation is conclusive. Several effects may contribute to the observation, depending on the experimental set-up:
• Definition of frozen: Is it the physical definition of the point at which water forms a visible surface layer of ice, or the point at which the entire volume of water becomes a solid block of ice? Some experiments have instead measured the time until the water reached 0°C.
• Evaporation: Reducing the volume to be frozen. Evaporation is endothermic, but this alone probably does not account for the entirety of the effect.
• Convection: Accelerating heat transfers. Reduction of water density below 4 °C (39 °F) tends to suppress the convection currents that cool the lower part of the liquid mass; the lower density of hot water would reduce this effect, perhaps sustaining the more rapid initial cooling. Higher convection in the warmer water may also spread ice crystals around faster.
• Frost: Has insulating effects. The lower temperature water will tend to freeze from the top, reducing further heat loss by radiation and air convection, while the warmer water will tend to freeze from the bottom and sides because of water convection. This is disputed as there are experiments that account for this factor.
• Supercooling: It is hypothesized that cold water, when placed in a freezing environment, supercools more than hot water in the same environment, thus solidifying slower than hot water. However, supercooling tends to be less significant where there are particles that act as nuclei for ice crystals, thus precipitating rapid freezing.
• Solutes: The effects of calcium, magnesium carbonate among others.
• The effect of heating on dissolved gases; however, this was accounted for in the original article by using boiled water.
It is very amazing to me as I cannot imagine hot water freezing faster than cold water. It seems almost impossible. Mpemba is curious and hence he managed to discover this theory. He is also very brave as he raised a question which other people thinks is ridiculous. So, to be an accomplished scientist, we must have a curious mind and is willing to learn more.
Oil Spill
Oil Spill off Singapore coast
A cargo tank on the Malaysian registered tanker MT Bunga Kelena 3 was damaged when, at around 6 a.m local time, the vessel collided with the MV Wally, a bulk carrier registered in St Vincent and the Grenadines, according to the Maritime and Port Authority of Singapore.
The spill, which took place eight miles (13 kilometres) off Singapore’s southeastern coast in the Traffic Separation Scheme, is estimated at 2000 metric tonnes, or about 14,660 barrels. The TSS runs along the Straits of Malacca and Singapore.
Four patrol and emergency response vessels and three private craft equipped with oil-spill equipment have been sent to the affected zone.
Nobody was injured and ship traffic was not affected by the incident, which took place eight miles (13 kilometres) off Singapore’s southeastern coast in the Traffic Separation Scheme, which runs along the Straits of Malacca and Singapore. Singapore is Asia’s biggest oil-trading and storage centre.
Both vessels were anchored off Singapore, Asia’s biggest oil trading and storage centre, after the accident and neighbouring Malaysia and Indonesia have been notified, the MPA said.
Impact of oil spills on marine life
The Malaysian Natural Resources and Envi¬ronment Minister Datuk Douglas Uggah Embas said on 2 Jun that the oil spill "appears to have no lasting effect on the affected coastal areas". He said "Once the beach has been cleaned, there is no effect and no more odour of oil because the sea current is moving and there is clean water flowing in". Adding he could see the difference between one spot
Peter Ng, director, Raffles Museum of Biodiversity Research, said on 30 May: "In the short term, some animals will die. We have not seen mass kills but I'm sure some are affected". The breathing of fishes, for example, will be affected if their gills are coated with oil. "(In the) longer term, the oil will affect the animals and plants in different ways. It may reduce the reproduction, it may reduce the growth rate, it might reduce their strength. And that has long-term implications."
Marine biologist Prof Chou Loke Ming explains that when oil slicks hit, they prevent corals from getting enough sunlight, cut off oxygen by coating plants and fish gills, and harbour volatile organic compounds that can poison marine life.
If most of the oil is removed, the impact from poisons and a lack of oxygen can be reduced, Professor Chou said, but spraying dispersant chemicals can break up the oil into smaller droplets which can sink to the bottom and affect marine life deeper in the sea.
In the longer term, how long will shores take to recover? Marine life may take three to four years, depending on the severity of the impact, Prof Chou said.
Commenting on how long oil from a spill lingers in the environment, climate expert Michael Totten, of international non-governmental organisation Conservation International, said that would depend on the type of oil, location, currents and weather conditions. For instance, more than 98 tonnes of oil from the 1989 Exxon Valdez spill off Alaska still lingers in the sands of Prince William Sound, as the remote area was hard for clean-up teams to reach.
Cleaning up oil
Cleaning up oil is tough at the beginning and gets harder every day. The first job is to contain a spill, a nearly impossible task in the real world.
On the water, booms which absorb and contain spills on relatively calm seas can be used to herd it into big pools that can be sucked up or burned. Chemical dispersants which separate crude into fine droplets can be sprayed from ships and planes. Rusty-colored oil 'mousse' is formed where dispersants mixed into the water by waves are breaking down the oil.
Above all, the oil needs to be kept off shore, which over time is the most difficult thing to do. When oil hits land it's often for a short visit -- dropping off a sheen and then moving with the tides up or down the shoreline. Eventually though, the oil ages, becoming a tar -- like a blob that gloms onto a surface and won't let go.
That's fine on a hard-packed sandy beach, which is the best place for an oil spill, since a careful lift of a thin layer of sand can get rid of most of the problem. But in marshes, new and old oil can spread thin and deep with a ferocity that makes any cleanup counterproductive -- boots kill more than the oil.
I hope that there will be no more oil spills in the future as it badly affects marine lives. Oil spills are harmful to the environment and needs effort to clean it up. It may take very long to clean up the oil spill even though not much oil are released into the sea. Hence I hope that ships would be more careful next time to avoid any collision.
A cargo tank on the Malaysian registered tanker MT Bunga Kelena 3 was damaged when, at around 6 a.m local time, the vessel collided with the MV Wally, a bulk carrier registered in St Vincent and the Grenadines, according to the Maritime and Port Authority of Singapore.
The spill, which took place eight miles (13 kilometres) off Singapore’s southeastern coast in the Traffic Separation Scheme, is estimated at 2000 metric tonnes, or about 14,660 barrels. The TSS runs along the Straits of Malacca and Singapore.
Four patrol and emergency response vessels and three private craft equipped with oil-spill equipment have been sent to the affected zone.
Nobody was injured and ship traffic was not affected by the incident, which took place eight miles (13 kilometres) off Singapore’s southeastern coast in the Traffic Separation Scheme, which runs along the Straits of Malacca and Singapore. Singapore is Asia’s biggest oil-trading and storage centre.
Both vessels were anchored off Singapore, Asia’s biggest oil trading and storage centre, after the accident and neighbouring Malaysia and Indonesia have been notified, the MPA said.
Impact of oil spills on marine life
The Malaysian Natural Resources and Envi¬ronment Minister Datuk Douglas Uggah Embas said on 2 Jun that the oil spill "appears to have no lasting effect on the affected coastal areas". He said "Once the beach has been cleaned, there is no effect and no more odour of oil because the sea current is moving and there is clean water flowing in". Adding he could see the difference between one spot
Peter Ng, director, Raffles Museum of Biodiversity Research, said on 30 May: "In the short term, some animals will die. We have not seen mass kills but I'm sure some are affected". The breathing of fishes, for example, will be affected if their gills are coated with oil. "(In the) longer term, the oil will affect the animals and plants in different ways. It may reduce the reproduction, it may reduce the growth rate, it might reduce their strength. And that has long-term implications."
Marine biologist Prof Chou Loke Ming explains that when oil slicks hit, they prevent corals from getting enough sunlight, cut off oxygen by coating plants and fish gills, and harbour volatile organic compounds that can poison marine life.
If most of the oil is removed, the impact from poisons and a lack of oxygen can be reduced, Professor Chou said, but spraying dispersant chemicals can break up the oil into smaller droplets which can sink to the bottom and affect marine life deeper in the sea.
In the longer term, how long will shores take to recover? Marine life may take three to four years, depending on the severity of the impact, Prof Chou said.
Commenting on how long oil from a spill lingers in the environment, climate expert Michael Totten, of international non-governmental organisation Conservation International, said that would depend on the type of oil, location, currents and weather conditions. For instance, more than 98 tonnes of oil from the 1989 Exxon Valdez spill off Alaska still lingers in the sands of Prince William Sound, as the remote area was hard for clean-up teams to reach.
Cleaning up oil
Cleaning up oil is tough at the beginning and gets harder every day. The first job is to contain a spill, a nearly impossible task in the real world.
On the water, booms which absorb and contain spills on relatively calm seas can be used to herd it into big pools that can be sucked up or burned. Chemical dispersants which separate crude into fine droplets can be sprayed from ships and planes. Rusty-colored oil 'mousse' is formed where dispersants mixed into the water by waves are breaking down the oil.
Above all, the oil needs to be kept off shore, which over time is the most difficult thing to do. When oil hits land it's often for a short visit -- dropping off a sheen and then moving with the tides up or down the shoreline. Eventually though, the oil ages, becoming a tar -- like a blob that gloms onto a surface and won't let go.
That's fine on a hard-packed sandy beach, which is the best place for an oil spill, since a careful lift of a thin layer of sand can get rid of most of the problem. But in marshes, new and old oil can spread thin and deep with a ferocity that makes any cleanup counterproductive -- boots kill more than the oil.
I hope that there will be no more oil spills in the future as it badly affects marine lives. Oil spills are harmful to the environment and needs effort to clean it up. It may take very long to clean up the oil spill even though not much oil are released into the sea. Hence I hope that ships would be more careful next time to avoid any collision.
Blank Cells
Stem cells are undifferentiated or ‘blank’ cells found in the human body that have the potential to develop into many different cell types that carry out different functions. Most cells in the human body are differentiated. That means they are built to function in a particular organ system and carry out a specific function. A red blood cell, for example, is designed to carry oxygen, while a white blood cell is designed to fight off disease. These differentiated cells result from the process of cell division, a process that begins with undifferentiated stem cells.
Pluripotent stem cells, found in embryos, can give rise to all the cells found in the human body – cells as diverse as those found in the brain, bone, heart and skin.
Multipotent stem cells, found in adults or in babies' umbilical cords, have a more limited capacity. Their development is limited to the cells that make up the organ system that they originated from. For example, a multipotent stem cell in the bone marrow can develop into a red blood cell, a blood platelet or a white blood cell, but not into a skin cell or brain cell.
Researchers believe that stem cells, especially pluripotent stem cells, hold much potential for medical therapies and medical research such as:
• Growing replacement cells or whole replacement organs. Human stem cells can be used to generate specialized cells in a laboratory and then be transplanted to replace damaged cells in the body. These could be used to treat a range of conditions from Parkinson disease to heart failure to spinal injuries. For example, in the case of a spinal injury, neural stem cells could be generated to replace damaged tissue.
• "Patching" organs that don't work properly - like helping a diabetic person's pancreas produce insulin. The newest therapies in research on stem cells and diabetes involve generating islet cells that produce insulin to replace those that a diabetic person’s immune system destroys.
• In the study of human development, stem cells could help researchers determine why, in the early stages of development, some cells become cancerous or how genetic diseases develop. This could lead to answers as to how they might be prevented.
• For research purposes, stem cells may be useful as a testing ground for new drugs before they are used on humans. Stem cells may be more accurate for research results than using animal subjects, as well as solve the ethical dilemma of using animals for medical testing.
Stem cell research has the potential to bring new treatment options to patients with Alzheimer's, Parkinson's disease, heart disease, burns, diabetes, and spinal cord injuries.
Ethical Issues
Research that uses multipotent stem cells (which are found in adults and in umbilical cords) is not generally considered controversial. However, because their ability to differentiate is limited, so is their usefulness in research.
However, research with pluripotent stem cells is controversial because it requires destroying an artificially-fertilized embryo at the 5-14 day stage. Because pluripotent stem cells can differentiate into all the cell types in the human body, they have the greatest application in research for new medical treatments.
Recently, researchers at the biotech company, Advanced Cell Technology, claim to have succeeded in harvesting stem cells from mouse embryos without killing them. If this technique is valid and its reliability improved, it could alleviate many of the ethical problems related to stem cell research.
I find this very interesting as I did not know that human stem cells can have so many uses and function. However I feel that there should not be a research with pluripotent stem cells as it requires destroying an artificially-fertilized embryo. I hope that the researchers would find how to harvest stem cells from human embryos without killing them just like what they did with the mouse embryos as soon as possible as it could alleviate many of the ethical problems related to stem cell reasearch.
Pluripotent stem cells, found in embryos, can give rise to all the cells found in the human body – cells as diverse as those found in the brain, bone, heart and skin.
Multipotent stem cells, found in adults or in babies' umbilical cords, have a more limited capacity. Their development is limited to the cells that make up the organ system that they originated from. For example, a multipotent stem cell in the bone marrow can develop into a red blood cell, a blood platelet or a white blood cell, but not into a skin cell or brain cell.
Researchers believe that stem cells, especially pluripotent stem cells, hold much potential for medical therapies and medical research such as:
• Growing replacement cells or whole replacement organs. Human stem cells can be used to generate specialized cells in a laboratory and then be transplanted to replace damaged cells in the body. These could be used to treat a range of conditions from Parkinson disease to heart failure to spinal injuries. For example, in the case of a spinal injury, neural stem cells could be generated to replace damaged tissue.
• "Patching" organs that don't work properly - like helping a diabetic person's pancreas produce insulin. The newest therapies in research on stem cells and diabetes involve generating islet cells that produce insulin to replace those that a diabetic person’s immune system destroys.
• In the study of human development, stem cells could help researchers determine why, in the early stages of development, some cells become cancerous or how genetic diseases develop. This could lead to answers as to how they might be prevented.
• For research purposes, stem cells may be useful as a testing ground for new drugs before they are used on humans. Stem cells may be more accurate for research results than using animal subjects, as well as solve the ethical dilemma of using animals for medical testing.
Stem cell research has the potential to bring new treatment options to patients with Alzheimer's, Parkinson's disease, heart disease, burns, diabetes, and spinal cord injuries.
Ethical Issues
Research that uses multipotent stem cells (which are found in adults and in umbilical cords) is not generally considered controversial. However, because their ability to differentiate is limited, so is their usefulness in research.
However, research with pluripotent stem cells is controversial because it requires destroying an artificially-fertilized embryo at the 5-14 day stage. Because pluripotent stem cells can differentiate into all the cell types in the human body, they have the greatest application in research for new medical treatments.
Recently, researchers at the biotech company, Advanced Cell Technology, claim to have succeeded in harvesting stem cells from mouse embryos without killing them. If this technique is valid and its reliability improved, it could alleviate many of the ethical problems related to stem cell research.
I find this very interesting as I did not know that human stem cells can have so many uses and function. However I feel that there should not be a research with pluripotent stem cells as it requires destroying an artificially-fertilized embryo. I hope that the researchers would find how to harvest stem cells from human embryos without killing them just like what they did with the mouse embryos as soon as possible as it could alleviate many of the ethical problems related to stem cell reasearch.
Acre
Origin:
The word "acre" is derived from Old English æcer originally meaning "open field", cognate to west coast Norwegian ækre and Swedish åker, German acker, Latin ager, and Greek αγρος (agros). The acre was approximately the amount of land tillable by one man behind an ox in one day. This explains one definition as the area of a rectangle with sides of length one chain and one furlong. A long narrow strip of land is more efficient to plough than a square plot, since the plough does not have to be turned so often. The word "furlong" itself derives from the fact that it is one furrow long. Before the enactment of the metric system, many countries in Europe used their own official acres. These were differently sized in different countries, for instance, the historical French acre was 4,221 square meters, whereas in Germany as many variants of "acre" existed as there were German states. Historically, the size of farms and landed estates in the United Kingdom was usually expressed in acres (or acres, roods, and perches), even if the number of acres was so large that it might conveniently have been expressed in square miles. For example, a certain landowner might have been said to own 32,000 acres of land, not 50 square miles of land.
Relation to SI unit:
1 international acre is equal to the following metric units:
• 4,046.8564224 square metres
• 0.40468564224 hectare (A square with 100 m sides has an area of 1 hectare.)
1 United States survey acre is equal to:
• 4,046.87261 square metres
• 0.404687261 hectare
1 acre (both variants) is equal to the following customary units:
• 66 feet × 660 feet (43,560 square feet)
• 1 chain × 10 chains (1 chain = 66 feet = 22 yards = 4 rods = 100 links)
• 1 acre is approximately 208.71 feet × 208.71 feet (a square)
• 4,840 square yards
• 160 perches. A perch is equal to a square rod (1 square rod is 0.00625 acre)
• 10 square chains
• 4 roods
• A chain by a furlong (chain 22 yards, furlong 220 yards)
• 1/640 (0.0015625) square mile (1 square mile is equal to 640 acres)
Disadvantages over other units:
It would be difficult to calculate the exact amount of acre as it has a lot of decimal points hence I feel that using square metres would be easier to use compared to acre.
The word "acre" is derived from Old English æcer originally meaning "open field", cognate to west coast Norwegian ækre and Swedish åker, German acker, Latin ager, and Greek αγρος (agros). The acre was approximately the amount of land tillable by one man behind an ox in one day. This explains one definition as the area of a rectangle with sides of length one chain and one furlong. A long narrow strip of land is more efficient to plough than a square plot, since the plough does not have to be turned so often. The word "furlong" itself derives from the fact that it is one furrow long. Before the enactment of the metric system, many countries in Europe used their own official acres. These were differently sized in different countries, for instance, the historical French acre was 4,221 square meters, whereas in Germany as many variants of "acre" existed as there were German states. Historically, the size of farms and landed estates in the United Kingdom was usually expressed in acres (or acres, roods, and perches), even if the number of acres was so large that it might conveniently have been expressed in square miles. For example, a certain landowner might have been said to own 32,000 acres of land, not 50 square miles of land.
Relation to SI unit:
1 international acre is equal to the following metric units:
• 4,046.8564224 square metres
• 0.40468564224 hectare (A square with 100 m sides has an area of 1 hectare.)
1 United States survey acre is equal to:
• 4,046.87261 square metres
• 0.404687261 hectare
1 acre (both variants) is equal to the following customary units:
• 66 feet × 660 feet (43,560 square feet)
• 1 chain × 10 chains (1 chain = 66 feet = 22 yards = 4 rods = 100 links)
• 1 acre is approximately 208.71 feet × 208.71 feet (a square)
• 4,840 square yards
• 160 perches. A perch is equal to a square rod (1 square rod is 0.00625 acre)
• 10 square chains
• 4 roods
• A chain by a furlong (chain 22 yards, furlong 220 yards)
• 1/640 (0.0015625) square mile (1 square mile is equal to 640 acres)
Disadvantages over other units:
It would be difficult to calculate the exact amount of acre as it has a lot of decimal points hence I feel that using square metres would be easier to use compared to acre.
Pound
Origin:
The unit is descended from the Roman libra (hence the abbreviation lb); the name pound is a Germanic adaptation of the Latin phrase libra pondo 'a pound weight'
Relation to SI unit:
SI unit for mass is kilogram. One pound is equal to 0.45359237 kilograms which is equivalent to 453.59237 grams.
Disadvantages over other units:
To me, I find that using kilogram would be easier to use compared to pound. The pound has too much decimal place so it would be difficult to use pound. It would be hard to be exact because if an object weighs 1.5kg, you will have a hard time calculating to find out the exact amount which is 3.306933933 pound.
The unit is descended from the Roman libra (hence the abbreviation lb); the name pound is a Germanic adaptation of the Latin phrase libra pondo 'a pound weight'
Relation to SI unit:
SI unit for mass is kilogram. One pound is equal to 0.45359237 kilograms which is equivalent to 453.59237 grams.
Disadvantages over other units:
To me, I find that using kilogram would be easier to use compared to pound. The pound has too much decimal place so it would be difficult to use pound. It would be hard to be exact because if an object weighs 1.5kg, you will have a hard time calculating to find out the exact amount which is 3.306933933 pound.
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