1. happyphysics.com Physics Lecture Resources Prof. Mineesh Gulati Head-Physics Wing Happy Model Hr. Sec. School, Udhampur, J&K Website: happyphysics.com

2. Ch 4 Newton’s Laws of Motion © 2005 Pearson Education

3. 4.1 Force and interactions Force is a vector quantity Force is a vector quantity SI unit of force is Newton SI unit of force is Newton Pulling force Pushing force © 2005 Pearson Education

5. Typical Force Magnitudes © 2005 Pearson Education

6. Same effect as F © 2005 Pearson Education

8. Net Force © 2005 Pearson Education

9. 4.2 Newton’s First Law A body acted on by no net force moves with constant velocity ( which may be zero) and zero acceleration A body acted on by no net force moves with constant velocity ( which may be zero) and zero acceleration F1 = F2 a = 0 In equilibrium © 2005 Pearson Education

10. Inertial Frames of Reference A frame of reference in which Newton’s first law is valid is called inertial frame of reference A frame of reference in which Newton’s first law is valid is called inertial frame of reference © 2005 Pearson Education

11. You and vehicle initially at rest You tend to remain at rest as the vehicle accelerates around you © 2005 Pearson Education

12. You and the vehicle are initially moving You tend to moving with constant velocity

13. 4.3 Newton ’ s second Law Constant v Increasing v Decreasing v © 2005 Pearson Education

14. Acceleration is proportio n al to net force © 2005 Pearson Education

15. Newton’s second Law If a net external force acts on a body, the body accelerates. The direction of acceleration is the same as the direction of the net force. The net force vector is equal to the mass of the body times the acceleration of the body. If a net external force acts on a body, the body accelerates. The direction of acceleration is the same as the direction of the net force. The net force vector is equal to the mass of the body times the acceleration of the body. © 2005 Pearson Education

17. 4.4 Mass and Weight © 2005 Pearson Education

18. Example 4.7 A 1.96x10 4 N Lincoln Town Car traveling in the +x-direction makes a fast stop; the x-component of the net force acting on it is -1.5x10 4 N. What is its acceleration? A 1.96x10 4 N Lincoln Town Car traveling in the +x-direction makes a fast stop; the x-component of the net force acting on it is -1.5x10 4 N. What is its acceleration? Ans: Ans: The mass of the car : The mass of the car : © 2005 Pearson Education

19. Newton’s Third Law If body A exerts a force on body B, then body B exerts a force on body A. These two forces have the same magnitude but are opposite in direction. These two forces act on different bodies. If body A exerts a force on body B, then body B exerts a force on body A. These two forces have the same magnitude but are opposite in direction. These two forces act on different bodies. © 2005 Pearson Education

21. Force diagrams © 2005 Pearson Education

22. Free body Diagrams mg N © 2005 Pearson Education

23. Summary

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