2. Forces and the Laws of Motion All of physics is either impossible or trivial. It is impossible until you understand it, and then it becomes trivial. -- Ernest Rutherford

3. Changes in Motion Force- push or pull exerted on some object Represents the interaction of an object with its environment

4. Forces cause changes in motion

5. Stationary object will move

6. Moving objects will stop

7. Objects can change direction

8. SI Unit of Force is the Newton Newton (N) 1 N = 1 kg x 1 m/s 2 Newton is the amount of force that causes a 1 kg object to accelerate 1 m/s 2

9. Forces can act through contact or at a distance Contact Forces- result from physical contact between two objects Field Forces- does not involve physical contact

10. The presence of an object affects the space around it so that a force is exerted on any other object placed within that space. The region of influence is called a field.

11. Force is a vector Assume that all forces act on a point at the center of an object

12. If Force is a Vector then the rules for Vector addition and subtraction still apply

14. Diagrams help analyze the situation Step 1: Draw the object, positioning it correctly

15. Next Step: draw and label vector arrows representing all external forces acting on the object 5800 N 14700 N 13690 N 775 N

16. Originate at the Center of the object Label size of the force Make sure only the forces acting on the car are included in your diagram 5800 N 14700 N 13690 N 775 N

17. Review FREE BODY DIAGRAM A critical first step for solving force problems 1. Draw a simple neat diagram that isolates the object whose motion is being analyzed. 2. Draw ALL the forces that act ON the object. 3. Do NOT draw any other forces. 4. Do NOT draw forces exerted BY the object on its surroundings.