2. Push Pull

3. force
A force is any push or pull that causes a resting object to move

4. force
A force is any push or pull that causes a resting object to move moving object to accelerate

5. Fundamental Forces
Gravity

6. Fundamental Forces
Electromagnetism

7. Fundamental Forces
Strong Nuclear

8. Fundamental Forces
Weak Nuclear

9. Contact Forces

10. Contact forces These are forces that require some contact
You push a cart – it moves
You catch a ball – it stops moving

11. At-a-distance Forces

12. At-a-distance forces These are forces that act without contact
The attraction of gravity
The repulsion of two poles of a magnet

13. Balanced Forces

14. Balanced force
A force in which the net force is equal to zero All the forces acting on an object must be taken into account

15. Balanced forces

16. UnBalanced force
A force in which the net force is greater than zero All the forces acting on an object must be taken into account

17. Unbalanced forces

18. Problem
Jimmy drops 5.0 kg box of shingles (50 N force) off the roof of his house into the swimming pool below. The box hits the water and encounters a 50 N force of resistance upward.

19. Which velocity-time graphs best describes the motion of the box?

20. Frictional Force

21. Friction force
A force that always opposes motion Static friction – the friction that is present between two stationary objects Kinetic Friction – the friction that develops between two moving surfaces

22. Friction force
Static

23. Friction force
Kinetic

24. Problem set balanced forces unbalanced forces

25. 1

26. 2

27. 3
If the net force acting upon an object is 0 N, the object MUST _____________. a. be moving erratically b . be accelerating c. be at rest d. be moving with a constant speed in the same direction e. either c or d

28. 4

29. 5

30. 6

31. Force symbolics

32. Applied Force
The force applied to an object by a person or another object
Our symbol: F

33. Gravity
The force that is directed "downward" towards the center of the Earth
Our symbol: W

34. Normal
The “support” force exerted upon an object that is in contact with another stable object.
Our symbol: N

35. Frictional
The force exerted by a surface that opposes the movement of an object across it.
Our symbol (static): fS
Our symbol (kinetic): fK

36. Air resistance
A special type of frictional force that acts upon objects as they travel through the air
Our symbol: Fair

37. Tension
The force transmitted through a string, rope, cable or wire when pulled tight by forces acting from opposite ends
Our symbol: T

38. Stop here