1. Chapter 4 Part 2: Work/Power Notes
What is Work?
Chapter 4
Part 2: Work/Power Notes

2. What is work calculated?
Work depends on two things:
Amount of force
Distance the object moves

3. What is work calculated?
Work = Force x Distance
Force is in Newtons (N)
Distance is in meters (m)
Work is in Joules (J)

4. Examples where force Changes?
How much work would you do if you used 300N of force to lift a plant onto a table that was 1.5m tall?
300N x 1.5m = 450J

5. Examples where force Changes?
How much work would you do if you used 600N of force to lift a plant onto a table that was 1.5m tall?
600N x 1.5m = J

6. Examples where distance changes?
How much work would you do if you used 800N of force to push a car a distance of 5m?
800N x 5m = 4,000J
5 meters

7. Examples where distance changes?
How much work would you do if you used 800N of force to push a car a distance of 10m?
800N x 10m = 8,000J
10 meters

8. How work Changes?
Force
If force _____, amount of work _____

9. How work Changes?
Distance
If distance _____, amount of work _____

10. Which one tires you out faster/more: walking or running up the stairs?
What is Power?
Imagine you carry a heavy TV up your stairs.
You walk up the stairs and it takes you 30 seconds to reach the top. You use a force of 500N to cover a distance of 4m. How much work did you do?
You run up the stairs and it takes you only 8 seconds to reach the top. You use a force of 500N to cover a distance of 4m. How much work did you do?
Which one tires you out faster/more:
walking or running up the stairs?

11. What is Power?
Power = the amount of work performed in a certain amount of time
When you run, you use the same amount of force just in a smaller amount of time
Therefore, you use more power

12. What is Power? You can change the amount of power by changing
The amount of force applied
The time covered
The distance in which the work is performed

13. How is Power calculated?
Power = Work / Time
Work is in joules (J)
Time is in seconds (s)
Power is in watts (W)

14. How is Power calculated?
Power = Work / Time
Work is in joules (J)
Time is in seconds (s)
Power is in watts (W)

15. How is Power calculated?
Power = Work / Time
Work is in joules (J)
Time is in seconds (s)
Power is in watts (W)

17. Example Problems?
A tow truck uses 11,000N of force to pull a car out of ditch. The truck moves the car a distance of 5m in 25 seconds. What was the power of the truck?

18. Example Problems?
You use 25N of force to carry your laundry basket up the stairs, a distance of 4m. This takes you 10 seconds to do. What was your power?

19. Example Problems?
What would happen to your power if you still used 25N of force to carry your laundry basket a distance of 4m but you ran up the stairs, decreasing your time to 3 seconds?