2. Work = when a force is applied on an object and it moves in the direction of the force.

3. Work = Force x distance W = F x d Joule = Newton x meter J = N x m

4. Do you do more work when you lift 80 N or when you lift 160 N?
Recall that work is force x distance! You do not have enough information to answer this question! What do you need to know?

5. Work depends on the distance!
W=80Nx1m=80J W=160Nx1m=160J W=80Nx2m=160J

6. Work input is the amount of work you put into a machine. Your effort
Work input is the amount of work you put into a machine.Your effort! Work output is the amount of work done by a machine .

7. Work output can never be greater than the work input. Why
Work output can never be greater than the work input. Why? Work in = 100 Joules Work out = 80 Joule
Work in
Work out
Machine
Heat
The other 20 J left the machine as heat!

8. Power is the rate at which work is done or how fast work is done.

9. Power = Work (W= F x d). time P = W P = F x d. t
Power = Work (W= F x d) time P = W P = F x d t t •  Measured in the unit Watt (W) named after James Watt the inventor of the steam engine.

10. How much power is required for a figure skater to lift his partner who weighs 400Newtons, 1 meter in 2 seconds? Power = work P = W (W = F x d) time t J = N x m

11. How much power is required for a figure skater to lift his partner who weighs 400Newtons, 1 meter in 2 seconds? P = 400 Newton x 1 meter 2 seconds P = 400 Joules seconds P = 200 Watts

12. Efficiency is a measure of how much of the work put into a machine is changed to useful work put out by a machine and is usually expressed as a percentage. Efficiency = Wout x 100% Win

13. How efficient is a machine that puts out 200 Joules of work when 250 Joules are put into it? Efficiency = Wout x 100% Win

14. How efficient is a machine that puts out 200 Joules of work when 250 Joules are put into it. Efficiency = Wout x 100% Win Efficiency = 200 x 100% Efficiency = .8 x 100% = 80 %

15. What happens to the other 20%?
Work in
Work out
Machine
Heat