1. Work and Machines

2. What is a machine? A device that allows you to do work in a way that is easier and more effective

3. How machines can help Machines make work easier by changing:  Amount of force you exert  Example : Lifting a piano to a moving truck vs pushing it up a ramp  Distance over which you exert a force  Example: Bicycle, you push the pedals a small distance but the bike moves a large distance  Direction in which you exert a force  Example: Flag pole, you pull down on the rope but the flag moves up

4. Input vs Output Force Input Force: The force YOU exert on a machine  Input Work = Input Force X Input Distance Output Force: The force the machine exerts on an object  Output Work = Output Force X Output Distance

5. Mechanical Advantage A machine’s mechanical advantage is the number of times a machine increases a force exerted on it. MA = Output Force / Input Force Example: You exert 15N of force on a can opener, the can opener exerts an output force of 30N on the can.  MA = 30N / 15N = 2 There is no unit for mechanical advantage because it is a multiple.

6. Efficiency of Machine The efficiency of a machine compares the output work to the input work. Efficiency = Output Work X 100% Input Work

7. Real vs Ideal Machines An ideal machine has an efficiency of 100%, but one does not exist In all machines some work is lost due to friction