1. STARTER
Can you fill in the energy transfer review sheet on your desks?
Work together as a group!

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

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

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

5. Work
For example, if Hina pushes a table, she is doing work against the friction force of the table against the floor.

6. 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)

7. Work done = Force x Distance
Another physics formula to learn!
Copy it down!!

8. Important!
The force has to be in the direction of movement.
Carrying your shopping home from Liverpool is not work in physics!
Not working

9. Remember! There are three key ingredients to work – force displacement
cause
In order for a force to qualify as having done work on an object, there must be a displacement and the force must cause the displacement.

10. Why am I doing this?
Group Activity: Read the statements below Which ones are examples of work being done?
Hina applies a force to a wall and becomes exhausted.
A book falls off a table and free falls to the ground.
A waiter carries a tray full of meals above his head straight across the room at constant speed.
A rocket accelerates through space.

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

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

13. Let’s look at some examples

14. GROUP CHALLENGE 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?

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?
Work = force x distance = 400 x 15 = 6000 J

16. GROUP CHALLENGE 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?

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?
Force = weight = 1200N
Work = F x d = 1200 x 2.5
Work = 3000 J

18. AIM: To investigate how hard we can work as a class!

19. Can you copy this please?
Name
Mass (kg)
Force (N)
Distance (m)
Work of one lift (J)
# of lifts in 1 min
Total work (J)
Mean Total Work for the group : J

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

21. Class results for each group
Mean Total work (J) 1 2 3 4 5
Class Mean: J
Conclusion:
Are we a hardworking class?

22. Let’s summarise! When Hina’s jokes get that bad
Have a go at some Work calculations on the WORK sheet
You must WORK INDIVIDUALLY!
(Your own WORK – so to speak!)
When Hina’s jokes get that bad