Simple Machines

• Make work easier

• Many are similar (are cousins of each other)

• Can be put together= compound machine

How do they make work easier?

1. By changing force needed to move something

2. By changing the direction of the force

3. Or by doing both

4. By changing the speed at which work is done

Mechanical Advantage

• The amount the force gets multiplied by a machine

• It is a ratio so it has no units

• Formula= Resistance (output) force divided by Effort (input) Force

Do machines allow you to multiply work?

• Work= energy

• Energy can not be multiplied, just used

• Efficiency compares work output to work input

• If they are efficient they _________?

• If they are not efficient (inefficient) they__?

Perpetual Motion?

• Perpetual means forever

http://www.kilty.com/pmotion.htm