PHYS 2211 Module 9.1

Linear Momentum

Recommended Reading

9.1 Linear Momentum

Learning Objectives

By the end of this section, you will be able to:

  • Explain what momentum is, physically
  • Calculate the momentum of a moving object

Linear Momentum

The linear momentum p of an object is the product of its mass and its velocity:

Practice 9.1.1
A 2.5-kg cart moving to the right (+x direction) with a speed of 12 m/s collides with a concrete wall and rebounds with a speed of 4 m/s. What is the change in momentum of the cart?
(a) 0
(b) −30 kg·m/s   
(c) −10 kg·m/s
(d) 40 kg·m/s
(e) −40 kg·m/s
Practice 9.1.2
If two particles have equal momentum, are their kinetic energies equal?
(a) yes, always
(b) no, never
(c) no, except when their masses are equal
(d) yes, as long as they move along parallel lines