1. 1 AP Physics Exam 2 Review Chapter 5-8

2. 2 Newton’s Three Laws of Motion 1 st :An object with no net force acting on it remains at rest or moves with constant velocity in a straight line. 2 nd : 3 rd :When one object exerts a force on a second object, the second object also exerts a force on the first object that is equal in magnitude but opposite in direction.  Action and reaction forces always exist together.

3. 3 Free Body (Force) Diagram Draw all forces acting on the object being considered – Ignore all forces this object acting on other objects – Draw forces starting from center of object or at points of action – Make sure each force giver can be identified

4. 4 Normal Force (N, but not Newton) Given by the surface in contact to support the object. N N N F app No contact  No normal force No tendency to move into surface  No normal force Always perpendicular to the surface in contact. Points from surface to the object

5. 5 Tension Tension is along the string and points away from the object of consideration. T

6. 6 Weight and Apparent Weight Apparent weight is either tension or normal force. T N Weight or gravity: gravitational force the Earth pulling on object around it  Always straight downward.

7. 7 Two kinds of frictions  Static friction:  Kinetic (or sliding) friction:

8. 8 Examples of centripetal forces Rounding a curve in a car Max velocity w/o skidding – Flat curve: – Banked curve: Orbiting the Earth (Sun or other object) – Gravity N f W Static friction provides the centripetal force (when no skidding) a component of Normal force (net force) Rear View  N W No friction

9. 9 Kinetic Energy, K Kinetic Energy: ability to do work due to motion

10. 10 Work Done by A Constant Force W: a scalar, no direction W 90 o. F d 

11. 11 Work-Kinetic Energy Theorem The total work done on an object is equal to the change in the kinetic energy of that object

12. 12 Work (W g ) Done by Weight (F g )

13. 13 Work Done by a Variable Force 1-D or: Area under curve of Force-position graph

14. 14 Spring Force and Work Hook’s Law: Spring force is given by  Notice that this force is the force exerted by the spring, not the force you apply to compress or stretch the spring. Work done by spring force:

15. 15 Power Average Power: Instantaneous Power:

16. 16 Potential Energy U (U g or U sp ) Gravitational Potential Energy: Spring (Elastic) Potential Energy:

17. 17 Force and Potential Energy For each potential energy, there is a conservative force associated with it.

18. 18 (Total) Mechanical Energy, E Sum of kinetic and potential energy: or simply,

19. 19 Conservation of Mechanical Energy When only conservative forces are doing work within a system, the kinetic energy and potential energy can change. However, their sum, the mechanical energy E of the system, remains unchanged.

20. 20 Work Done By External Force Work done by external force will change the total mechanical energy of the system: If there is also kinetic friction, where is the heat gain (change in thermal energy) Total Energy: E int = Chemical Energy & Nuclear Energy

21. 21 Work and Energy Change Total work done by __________________________. Total work done by _______________________________. Work-Kinetic Energy Theorem: all external forces (excluding spring force and gravity) all external forces, normally including spring force and gravity.