The lever is a simple machine consisting of a bar supported at some stationary point along its length and used to overcome resistance at a second point by application of force at a third point. The stationary point of a lever is known as its fulcrum.
The Lever Principle has been found by experiment where two equal forces were acting in opposite directions, i.e., clockwise and counterclockwise, and applied to a uniform lever at equal distances from the fulcrum counteract each other and established a state of equilibrium, or balance, in the lever. Experiment has also shown that two unequal forces when acting in opposite directions will bring about an equilibrium when the product of the magnitude of one force and its effort arm, or lever arm (the distance of its point of application from the fulcrum), is equal to the product of the magnitude of the other force and its effort arm. In physics the product of a force by its effort arm is called moment of the force. The general conclusion known as the principle of moments states that equilibrium is established when the sum of the moments of the forces acting in a clockwise direction is equal to the sum of the moments of the forces acting in a counterclockwise direction. It is possible, as a result, to overcome a very large force at a short distance from the fulcrum with a very small force at a great distance from the fulcrum. Archimedes is supposed to have boasted, having the lever in mind, that given a place to stand he could move the Earth.
Friday, May 14, 2010
Summary
This term i have learnt many things. 1. SI units of mass, density, volume eg.
2.Formula for calculating the voulme of a sphere, cone, pyramid eg. 3. Formula for calculating pressure, density, work done, weight/force eg. 4. How to calculate moments 5. How to calculate force exerted on a lever 6. Instruments to measure- mass: spring balance eg. This is just a short summary of what we have learnt and most interestingly, we learnt many out of the textbook facts.
2.Formula for calculating the voulme of a sphere, cone, pyramid eg. 3. Formula for calculating pressure, density, work done, weight/force eg. 4. How to calculate moments 5. How to calculate force exerted on a lever 6. Instruments to measure- mass: spring balance eg. This is just a short summary of what we have learnt and most interestingly, we learnt many out of the textbook facts.
Thursday, May 13, 2010
MEDICINE BALLS!
Medicine balls are generally constructed of a leather or vinyl covered nylon cloth, and filled with impact absorbing materials to give them weight. Vinyl covered medicine balls typically are sand filled and are not used for exercises requiring bouncing. Sand or steel shot filled neoprene bags are also used for medicine ball exercises not requiring bouncing.[1]
Some medicine balls have an inner half sphere of dense material in varying thicknesses and seamed together with an outer rubber shell. Other medicine balls have a thin rubber bladder covered by a thick rubber outer surface. Medicine balls that are constructed with an inner rubber bladder and rubber outer surface incorporate an air valve to pump up the ball and increase the bounce. The outer rubber surface has indented designs for easy handling. Over time the rubber surface may wear down if the medicine ball has been used on rough surfaces.
Other types of medicine ball include balls made of gel-filled polyvinyl chloride shells, balls made of solid polyurethane, and neoprene bags filled with sand or steel shot. The materials can vary depending on the desired weight and density.
A basketball can be filled with sand, stitched shut, and used as an effective low-price medicine ball where resources are scarce, and is popular in, for example, home "garage" gymnasia.
www.wikipedia.org
Some medicine balls have an inner half sphere of dense material in varying thicknesses and seamed together with an outer rubber shell. Other medicine balls have a thin rubber bladder covered by a thick rubber outer surface. Medicine balls that are constructed with an inner rubber bladder and rubber outer surface incorporate an air valve to pump up the ball and increase the bounce. The outer rubber surface has indented designs for easy handling. Over time the rubber surface may wear down if the medicine ball has been used on rough surfaces.
Other types of medicine ball include balls made of gel-filled polyvinyl chloride shells, balls made of solid polyurethane, and neoprene bags filled with sand or steel shot. The materials can vary depending on the desired weight and density.
A basketball can be filled with sand, stitched shut, and used as an effective low-price medicine ball where resources are scarce, and is popular in, for example, home "garage" gymnasia.
www.wikipedia.org
SUPER GLUE!!!!
Super glue also known as Cyanoacrylate which is the generic name for cyanoacrylate based fast-acting adhesives such as methyl 2-cyanoacrylate, ethyl-2-cyanoacrylate (commonly sold under trade names like SuperGlue and Krazy Glue), n-butyl cyanoacrylate (used in the veterinary glues Vetbond and LiquiVet and skin glues like Indermil and Histoacryl). 2-octyl cyanoacrylate is a medical grade glue encountered under various trade names; e.g., LiquiBand, SurgiSeal, FloraSeal, Dermabond, and Nexaband. Cyanoacrylate adhesives are sometimes known as "instant glues". The abbreviation "CA" is commonly used for industrial grades.
Tuesday, May 11, 2010
What i have learnt this term
Something interesting i learnt from Mr lyndon lim, is that not all parts of the school has equal stability. He said that the toilet has the least stability and if too many girls are in one cubicle, for all we know the floor might crack and just fall causing serious damage. During lessons, we have watched many airplane videos and i have gained much knowledge from them. Some of them teached me about how the planes work. One example is that there are small turbines that generate electricity when the plane has run out of fuel. Another example is how the fuel engines work- X-feed and so on. In all, iwould like to continue in ESP and learn more interesting stuff/ facts.
Friday, May 7, 2010
How to make bath salt
Materials:
Bottle or Jar
Epsom Salts
Food Coloring
Perfume or Essential Oil
Instructions:Combine the desired amount of Epsom salts (enough to fit in your bottle or jar) with food coloring. Mix well so color is even. Add your perfume or essential oil and mix again. Spread the mixture out on a sheet of wax paper to dry for a couple of hours and then put it in the bottle or jar.
While the salts can be used right away, the perfume or essential oil will blend better with the salt if it is allowed to set in the jar for a few weeks.
Bottle or Jar
Epsom Salts
Food Coloring
Perfume or Essential Oil
Instructions:Combine the desired amount of Epsom salts (enough to fit in your bottle or jar) with food coloring. Mix well so color is even. Add your perfume or essential oil and mix again. Spread the mixture out on a sheet of wax paper to dry for a couple of hours and then put it in the bottle or jar.
While the salts can be used right away, the perfume or essential oil will blend better with the salt if it is allowed to set in the jar for a few weeks.
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