1. Physics 11 Dynamics IV Mr. Jean

2. The plan: Video clip of the day Friction Problems Net Forces Return Unit Test Practice Questions

3. Normal Force (F n ): The normal force is the component, perpendicular to the surface of contact. Example: the surface of a floor is preventing the object from penetrating the surface. The floor supplies the normal force.

4. Surface Friction ( F f ): The magnitude of the force of surface friction is the product of the coefficient of friction and the magnitude of the normal force. The direction of the force of friction is always opposite to the direction of the motion.

6. Free-Body Force Diagrams: http://www.physicsclassroom.com/class/ne wtlaws/u2l2c.cfmhttp://www.physicsclassroom.com/class/ne wtlaws/u2l2c.cfm Let’s take 15 minutes to try the following questions. Draw the FULL free body. –All forces –Labelled with SI units –All masses and KNOWN variables

12. Net Forces: The existence of an unbalanced force for a given situation can be quickly realized by looking at the free-body diagram for that situation.

13. Brightstorm Videos: Net Forces: http://www.brightstorm.com/science/physic s/newtons-laws-of-motion/net-force- resultant-force/ http://www.brightstorm.com/science/physic s/newtons-laws-of-motion/net-force- resultant-force/ http://www.youtube.com/watch?v=AFnoBr hOR4Uhttp://www.youtube.com/watch?v=AFnoBr hOR4U

14. Consider the following forces:

15. Consider the following force diagrams:

16. Solutions:

17. Determine the Net Forces:

18. Solutions:

19. Determine the acceleration if the object had a mass of 2kg:

20. Solutions:

21. Net Forces: