Chapter 9 Objectives: 1) Define momentum. 2) Be able to calculate momentum and include the appropriate units with your answer. 3) Know what “impulse” is and how momentum can be changed. 4) Explain the conditions under which momentum is conserved. 5) Be able to solve conservation of momentum problems. 6) Compare and contrast “elastic collisions” and “inelastic collisions.”

Chapter 9 “Momentum and Its Conservation” I) Impulse and Momentum A) Impulse and Momentum Momentum: The product of an object’s _ _ _ _ and _ _ _ _ _ _ _ _ .

a) The Equation: b) The Units:

c) Sample Problem: What velocity must a car with a mass of 1210 kg have in order to have the same momentum as a pickup truck with a mass of 2250 kg traveling at 25 m/s?

2) Change in Momentum: a) _____________: a change in the momentum of an object due to the force acting on the object for a given amount of time. b) The Equation c) The Units

B) Using the Impulse-Momentum Theory *How do airbags work in cars???

1) Sample Problem: A 2,500 kg car traveling North is slowed from an initial velocity of 20.0 m/s by a 6,250 N braking force. Use the Impulse-Momentum Theory to answer the following: a) What is the car’s velocity after 2.50 s? b) How long will it take to stop the car?

II) Conservation of Momentum A) Two-Particle Collisions *Demo the “collision balls” apparatus!

1) Law of Conservation of Momentum: The total momentum of all objects interacting with each other remains conserved regardless of the nature of the forces between them. a) The Equation:

2) Sample Problem: A 63.0 kg astronaut is on a space walk when the tether line to the shuttle breaks. The astronaut is able to throw a 10.0 kg oxygen tank in a direction away from the shuttle with a speed of 12.0 m/s, propelling the astronaut back to the shuttle. Find the final velocity of the astronaut after throwing the oxygen tank.

B) Collisions 1) Types of collisions a) _____________ Collision: a collision in which objects REBOUND after colliding. Example:

b) _____________ Collision: a collision in which the colliding objects couple (stick together) after colliding. Example:

2) The Law of Conservation of Momentum and Collisions: a) Elastic Collisions:

b) Inelastic Collisions:

c) Sample Problem: A 1,500 kg car traveling at 15 c) Sample Problem: A 1,500 kg car traveling at 15.0 m/s collides with a 4,500 kg truck that is at stopped at a light. After colliding the car and truck become entangled at the bumpers. What will be their velocity after the collision?