Physics Honors/AP 1 and 2

Homework

# Physics 7: 5-10 Elastic and Inelastic Collisions

## Homework

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 7: 5-10

##### Study Points
• Section 7.5: When we apply the conservation of momentum and the conservation of energy simultaneously to the linear collision of two objects, we discover that the relative speeds of two colliding object before and after a collision are equal and opposite: V1 - v2 = -(v'1 -v'2), regardless of the masses of the objects m1 and m2.
• Section 7.6: In inelastic collisions, masses which are separate prior to the collision become joined after the collision, but the laws of momentum and energy conservation still hold. The sum of energies prior to the collision and the sum of energies after the collision must balance, as must the total before-and-after momenta.
• Section 7.7: We can solve collisions in 2 or 3 dimensions by breaking down the velocities into coordinate components and solving the momentum in each direction separately, then adding the components back together to find the net velocities.
• Section 7.8: When we consider the translational motion of a body, we can treat it as though all the mass of the body were concentrated at one point, the "center of mass".
• Section 7.9: Because the motion of the human body has been well-studied, there are rules for finding the centers of mass of different body parts in a typical adult body. We can use these to predict how humans move.
• Section 7.10 We must use center-of-mass calculations in accounting for the motions of an object which disintegrates in motion while under the influence of an outside force. If we sum up the motions and velocities of all the pieces, they will add up to the predicted motion of the center of mass.

### Key Equations

• Velocities in elastic collisions
• Velocities in inelastic collisions
• Center of Mass

### Web Lecture

Read the following weblecture before chat: Collisions in One Dimension

### Study Activity

Use the Collision Carts Simulation to explore elastic and inelastic collisions. Try to complete Exercises 1 and 2.

Physics Interactive is hosted by the Physics Classroom.

### Chat Preparation Activities

• Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

### Chapter Quiz

• Required: Complete the Mastery exercise with a passing score of 85% or better.
• Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!

### Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!