Work is the transfer of energy to an object by using a force that causes the object to move in the direction of the force. * Work is measured is Joules

W = F x D Work = force times distance

Is doing homework really work?

Example: Using a 10N force, you push a shopping card 8M How much work do you do? W = F x D W = 10N x 8 M W = 80 J

Power is the rate at which work is done P = W/T Power =Work / Time Power is the rate at which work is done P = W/T Power =Work / Time *Power is measured in Watts

A machine is a device that make works easier by changing the size or direction of the force.

A simple machine is a device that does work with only one movement.

A compound machine is a combination of 2 or more simple machines.

Remember the Law of Conservation of Energy: Energy can neither be created or destroyed. However, energy can change from one form to another. ** You can never get more work out of a machine (work output) than you put into a machine (work input) because some energy is always lost to heat (friction)!!

Work done by the machine is called : Work Output Work that you do on a machine is called: Work Input Number of times the machine multiplies force is called: Mechanical Advantage

Levers: a bar that is free to pivot or turn about a fixed point (fulcrum). 1st class lever: fulcrum is in the middle and the load and effort is on each side. ie) see-saw 2nd class lever: fulcrum and effort are at opposite ends, with the load in the middle. ie) wheelbarrow 3rd class lever: fulcrum and load are at opposite ends and the effort is in the middle ie) stapler

Mechanical adavantage (MA) = Output Force Input Force Mechanical Efficiency is the mechanical advantage in percentage form. ie) Sam is wanting to see which chainsaw is the most efficient. How would he do that using the information below: Chainsaw A : Work input = 1500 J Work output = 1342 J Chainsaw B: Work input = 1610 J Work output = 1500 J Chainsaw A: 1342 J = 89% 1500 J Chainsaw B: 1500 J = 93% 1610 J