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. 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? no workwork

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? Who has to use more force to move the barrel? Work = 6m x 2N Work = 3m x 4N Work = 12J 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. object’s motion pushing force

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.

26. Ramp or No Ramp Materials blockspring scale boardmeter stick Procedure 1. Attach the block with the eyelet to the spring scale. 2. Using the spring scale, lift the block into the air to a height of.5m (50cm). Record how much force was used. Make sure you read the spring scale during the lift, not when you stop at.5m. 3. Build an inclined plane (ramp) with a height of.5m. Record the length of the inclined plane. 4. Attach the spring scale to the block with the eyelet and pull it up the ramp. 5. Record the amount of force it took to move the shoe.