click below
click below
Normal Size Small Size show me how
K.L. chapter 8
Work and Machines
| Word | Defintion |
|---|---|
| Work | The transfer of energy to an object by using a force that causes the object to move in the direction of the force. |
| Joule | The unit used to express energy; equivalent to the amount of work done by a force of 1 N acting through a distance of 1m in the direction of the force (symbol,j) |
| Power | The rate at which work is done or energy is transformed. |
| Watt | The unit used to express power; equivalent to joules per second (symbol, W) |
| Machine | A device that helps do work by either overcoming a force or changing the direction of the applied force. |
| Work input | The work done on a machine; the product of the input force and the dustance through which the force is exerted. |
| work output | The work done by a machine; the product of the output force and the distance through which the force is exerted. |
| Mechanical advantage | A number that tells how many times a machine multiplies force. |
| Mechincal efficiency | A quantity, usually expressed as a percentage, that measures the ratio of work output to work input; it can be calculated by dividing work output by work input. |
| Lever | A simple machine that consists of a bar that pivots at a fixed point called a fulcrum. |
| Pulley | A simple machine that consists of a wheel over which a rope, chain,or wire passes. |
| Wheel and Axle | A simple machine consisting of two circular objects of different sizes; the wheel is the larger of the two circular objects. |
| Inclined plane | A simple machine that is a straight, slanted surface, which facilitates the raising of loads; a ramp. |
| Wedge | A simple machine that is made up of two inclined planes and that moves; often used for cutting. |
| Screw | A simple machine that consists of an inclined plane wrapped around a cylinder. |
| Compound Machine | A machine made of more than one simple machine. |