1. Physics 151 Week 7 Day 1 Topics  Newton’s 1st Law of Motion  Newton’s 2nd Law of Motion  Newton’s 3rd Law of Motion  Practice with Free-Body Diagrams & System Schema  Momentum  Impulse  Impulse-momentum Theorem  Conservation of Momentum

2. Newton's Laws of Motion Slide 4-19 Newton 0th Law Objects are dumb - They have no memory of the past and cannot predict the future. Objects only know what is acting directly on them right now Newton's 1st Law An object that is at rest will remain at rest and an object that is moving will continue to move in a straight line with constant speed, if and only if the sum of the forces acting on that object is zero. Newton's 2nd Law acceleration of an object = sum of forces acting on that object / the mass of the object Newton's 3rd Law Recall that a force is an interaction between two objects. If object A exerts a force on object B then object B exerts a force on object that is in the opposite direction, equal in magnitude, and of the same type.

3. An elevator, lifted by a cable, is going up at a steady speed. Identify the forces acting on the elevator. Is T greater than, equal to, or less than w? Or is there not enough information to tell? A => F T > F g B => F T = F g C => F T < F g Example Problem Slide 4-30

4. An elevator, lifted by a cable, is going up at a steady speed. Identify the forces acting on the elevator. Is T greater than, equal to, or less than w? Or is there not enough information to tell? A => F T > F g B => F T = F g C => F T < F g Example Problem Slide 4-30

5. Newton's First Law of Motion Demonstrations DEMO - Smash the HAND DEMO - Tablecloth DEMO - Pull the string

6. Impulse The force of the foot on the ball is an impulsive force. Slide 9-8

7. Graphical Interpretation of Impulse J = Impulse = area under the force curve Slide 9-9

8. Momentum Momentum is the product of an object’s mass and its velocity: Slide 9-10 p = mv 

9. The Impulse-Momentum Theorem Impulse causes a change in momentum: Slide 9-11 J =p f - p i = ∆p  

10. Newton's Third Law of Motion Demonstrations DEMO - Pushing off the wall DEMO - Force Probes One probe pushing the other DEMO - Force Probes One probe pulling the other DEMO - Force Probes & Collisions I Moving & Stationary Cart Heavier vs. Lighter Cart

11. Newton’s 3rd Law Demonstrations Slide 4-19 A.F A=>B > F B=>A B. F A=>B A C. F A=>B = F B=>A D. Not enough information given to tell

12. In terms of the initial and final total momenta: The Law of Conservation of Momentum In terms of components: Slide 9-18 P f = P i 