Study Guide for Simple Machines

Work - Is done when a force causes an object to move in the direction of the force.

Simple Machine - make work easier; NOT LESS WORK

Work = Force (N) x Distance (m)

Example: You push a box with 8N of force and the box moves 6m. How much work is done?

8N x 6N = 48J of Work

Power is the rate at which work is done. The faster you complete work, the more power you are generating.

Power (watts) = Work (J) / Time (s)

Example: You sand a piece of wood doing 45J of work in 5 seconds. How much power did you generate?

45J / 5 s = 9 watts

Machine - a device that makes work easier by changing the size or direction of the force.

Work Input - the amount of work you put into the machine.

Work Output - the amount of work done by the machine.

WORK OUTPUT CAN NEVER BE GREATER THAN WORK INPUT (FRICTION CAUSES THIS).

Mechanical Advantage - the number of times the machine multiplies force.

Mechanical Advantage = output force (N) / input force (N)

Mechanical Efficiency - work output/work input x 100 (measured as percentage %)

TYPES OF MACHINES

1st Class Lever - the fulcrum is between the input force and output force.

2nd Class Lever - fulcrum at one end with input force at the other end and output force in between.

3rd Class Lever - the input force is between the fulcrum and the output force.

Pulleys - a simple machine that has a grooved wheel and a rope or cable.

Wheel and Axle - simple machine consisting of two circular objects of two different sizes.

Incline Plane - a simple machine that is a straight slanted surface (ramp).

Wedges - a pair of inclined planes that move. (knife/axe)

Screws - an inclined plane wrapped around a cylinder.