1. WORK

2. Force
A push or pull
You exert force on a pencil when you write
Forces are described by how strong they are and in what direction they are going

3. Unbalanced Forces
Unbalanced forces on an object will change the object’s motion
Start moving
Stop moving
Change direction

4. Unbalanced Forces

6. Balanced Forces and Motion
Forces exerted on an object do not always change the objects motion
Balanced forces – equal forces acting in opposite directions
If forces are equal but opposite, the object will not move

7. Balanced Forces and Motion

8. Work
When you exert a force on an object and it moves

9. No Work Work Work is only done if an object moves some distance
Holding something is not work even though it makes you tired
No Work

10. Work
Work or no work?
work
work
no work
work

11. Force, Motion, and Direction
In order to work on an object, the force you exert must be in the same direction as the object’s motion

12. Force, Motion, and Direction
No Work

13. Force, Motion, and Direction
Some Work

14. Force, Motion, and Direction
All Work

15. Calculating Work
The amount of work done depends on both the amount of force you exert and the distance the object moves
Work is measured in joules
A joule is the amount of work you do when you exert 1 Newton of force to move an object 1 meter
Work = force x distance

16. Calculating Work
How much work is done if a 2N of force is used to move a box 4m?
Work = force X distance
Work = 2N x 4m
8 J

17. Calculating Work
A hydraulic lift exerts a force of 12,000N to lift a car 2m. How much work is done on the car?
Work = force X distance
24,000 J

18. Calculating Work
You exert a force of 0.2N to lift a pencil off the floor. How much work do you do if you lift it 1.5m?
Work = force X distance
.3 J

19. Who is doing more work to move the barrel?
Work = 6m x 2N
Work = 12J
Work = 3m x 4N
Work = 12J
Who is doing more work to move the barrel?
Who has to use more force to move the barrel?
They are doing the same amount
The man with the shorter ramp

20. Activity 1
Apply a quick push to the block of wood to make it move 100cm.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.
pushing force
object’s motion

21. Activity 2 Apply a force to the block to lift it 100cm.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

22. Activity 3 Apply a constant force to the block to move it 100cm.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

23. Activity 4 Hold a book at the same level for 15 seconds.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

24. Activity 5 Apply a constant downward force to the desk for 15 seconds.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

25. Activity 6 Apply a pull to the block to move it 100cm.
Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.