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Module 2

1. Module 2

1.7. Page 5

Lesson 1

Module 2—The Conservation of Momentum in Isolated Systems

Try This

 

Verify your answers, where possible, by using the Collision 1D simulator.

 

TR 1. When you shoot a gun, it "kicks back," or recoils.

  1. Using conservation of momentum, explain why a gun recoils when you shoot it.

  2. If a 30-g bullet is shot with a velocity of +300 m/s from a 7.5-kg gun, what is the recoil velocity of the gun?
Module 2: Lesson 1 Assignment

 

Remember to submit the answers to A 1 and A 2 to your teacher as part of your Module 2: Lesson 1 Assignment.

 

A 1. Object A, with a mass of 2.0 kg, is travelling to the right at 15.0 m/s. Object B, with a mass of 12.5 kg, is also travelling at 15.0 m/s, but to the left. If the two objects stick together upon impact, what is the final velocity of the system?

 

A 2. A 250-g firecracker explodes into two pieces. The first piece has a mass of 97 g and flies off to the right at 16 m/s. What is the velocity of the second piece?

 

Self-Check

 

SC 2. An object, initially travelling to the right, collides with another object that is at rest. After the collision, the objects stick together and move to the left. Is this collision possible? Explain why or why not.

 

Check your work.
Self-Check Answers

 

SC 2. This is not possible. The initial momentum of the system is to the right; therefore, the final momentum must also be to the right.

 

 

Module 2: Lesson 1 Assignment

 

Remember to submit the answers to A 3 to your teacher as part of your Module 2: Lesson 1 Assignment.

 

A 3. Are the following collisions possible? Explain why or why not.

  1. Object A, initially travelling to the right, collides with object B, which is at rest. After the collision, object A moves back to the left and object B remains at rest.

  2. Object A, initially travelling to the right, collides with object B, which is at rest. Object B has more mass than object A. After the collision, object A moves back to the left and object B moves to the right.

  3. An object is travelling to the right and collides with another object that is at rest. After the collision, both objects travel to the right, but at different speeds.
Read

 

Read “Momentum is Conserved in One-dimensional Collisions” on pages 473 to 475 of your physics textbook.

 

Newton’s second and third laws can be used to derive the equation for impulse. In fact Newton’s original writings defined force in terms of momentum and time, not the that we used in Physics 20. However you haven’t done the calculus that is required to understand Newton’s original definition of force.

 

Momentum and Newton's Law

 

Try This

 

TR 2. Answer questions 1, 2, 5, 6, and 7 of “9.3 Check and Reflect” on page 486 of your physics textbook.