1. Do now! Can you complete the questions on heat transfer that Mr Porter gave you last lesson? James Prescott Joule 1818-89

2. Today’s lesson Learn what “work” is! Learn how to calculate work See who can do the most work! If we have time we will look at power.

3. A reminder Energy cannot be made or destroyed, only transformed (changed). Energy is measured in Joules. That’s me!

4. Work In physics, work has a special meaning, different to “normal” English.

5. Work In physics, work is the amount of energy transformed (changed) when a force moves (in the direction of the force)

6. Work In physics, work is the amount of energy transformed (changed) when a force moves (in the direction of the force) Can you copy it down please?

7. Work For example, if Mr Porter pushes a table, he is doing work against the friction force of the table against the floor.

8. Calculating work The amount of work done (measured in Joules) is equal to the force used (Newtons) multiplied by the distance the force has moved (metres). Force (N) Distance travelled (m)

9. Work done = Force x Distance Another sexy physics formula to learn!

10. Work done = Force x Distance Can you copy it down please?

11. Important The force has to be in the direction of movement. Carrying the shopping home is not work in physics!

12. Lifting objects When we lift objects, we are doing work because a force is moving. Force Distance moved

13. Lifting objects Our lifting force is equal to the weight of the object. Lifting force weight

14. Let’s look at some examples

15. Work done (J) = Force (N) x distance (m) A woman pushes a car with a force of 400 N for a distance of 15m. How much work has she done?

16. Work done (J) = Force (N) x distance (m) A woman pushes a car with a force of 400 N for a distance of 15m. How much work has she done? Work = force x distance = 400 x 15 = 6000 J

17. Work done (J) = Force (N) x distance (m) A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do?

18. Work done (J) = Force (N) x distance (m) A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do? Force = weight = 1200N Work = F x d = 1200 x 2.5 Work = 3000 J

19. How much work can you do?

20. Can you copy this please? NameMass (kg) Force (N) Distance (m) Work of one lift (J) # of lifts in 1 min Total work (J)

21. Arm curls distance Force required = weight of object = mass (kg) x 10

22. Off you go! NameMass (kg) Force (N) Distance (m) Work of one lift (J) # of lifts in 1 min Total work (J)

23. Power!

24. Power is the amount of energy transformed (changed) per second. It is measured in Watts (1 Watt = 1 J/s) Power = Energy transformed time

25. Power For each of the people in your table, can you calculate their power?

26. Let’s do some more work! Let’s drown this dog we’ve found Pull!