1. Chapter 10 Section 1: The Nature of Force

2. What is force? A force is a push or a pull

3. All forces have a size and a direction

4. A force can change the acceleration of an object by either changing the speed or the direction of the object

5. The SI unit for force is the Newton (N) F = M(kg) x A(m/s²)

6. Forces acting in objects. All forces act on objects

7. For any push that occurs, something has to receive the push (You can’t push nothing!)

8. The same is true for any pull (eg) Some trains are so massive that extra locomotives are added until the net force provided by all the locomotive is large enough to move the train.

9. A force acting on an object does not mean motion will occur (eg) your exerting a force on the chair you are sitting on but it’s not moving because the floor is also exerting a force on the chair

10. You cannot always tell what is exerting a force or what is receiving a force. (eg) Gravity, Static Electricity, Magnetism

11. Determining Net Force Net Force is the combination of all the forces acting on an object.

12. Net force is determined by the direction of the forces

13. When forces act in the same direction, you add the forces to determine the net force. The net force will be in the same direction as the individual forces.

14. (eg) You and your Mom move the couch. You pull on one end of the couch with a force of 25 N and your Mom pushes on the other end on the couch with a force of 15 N. The forces are in the same direction so 25 + 15 = 40N of net force

15. When two forces act in opposite directions, you subtract the smaller force from the larger force to determine the net force. The net force will be in the same direction as the larger force

16. (eg) Team 8B and the 8B teachers have a Tug of War. Team 8b exerts a force of 100N to the left and the 8B teachers exert a force of 500N to the right (opposite direction of the students). The Net Force would be 500 – 100 = 400N to the right, and the students would fall in the mud!!

17. Force and Pressure are different. Pressure is the amount of force exerted on a given area.

18. (eg) Bed of Nails and Magician: What is the net force of an object when you combine a force of 7N north with a force of 5N south?

19. Balanced and unbalanced Forces If you know the net force acting on an object, you can determine the effect the net force will have on the object’s motion.

20. Net force tells you whether the forces acting on the object are balanced or unbalanced

21. When the net force equals zero the forces are balanced and the object will not change it’s motion. It will either stay in motion or it will remain at rest (eg) Light hanging from the ceiling(gravity pulling down = force of cord pulling up),

22. (eg) Bird’s nest in a tree, a hat on your head, a house of cards.

23. When the net force is greater than zero the forces are unbalanced and the object will produce a change in motion (speed/ direction) It will cause the object to speed up, slow down, stop, start, or change direction.

24. An object can continue to move when the unbalanced forces are removed. (eg) When a ball is kicked, it receives an unbalanced force, but continues to move long after the force of the kick has ended