Momentum and External Force

Description and Assumptions

This model is [generally applicable] (assuming knowledge of the external forces and system constituents).

Problem Cues

This model is especially useful when describing the momentum of systems where external forces are absent (system momentum will be constant) or estimating the force in a process that occurs in a very short time interval such as collisions (impulse will be easier to determine than force).

Learning Objectives

Students will be assumed to understand this model who can:

Define the momentum of a point particle.
Define impulse in terms of momentum or in terms of force.
Give an expression for the time-average force on a system in terms of its momentum.
Calculate the net external force on a system containing several objects.
Describe the conditions required for the momentum of a system to be conserved.
Describe the system that must be considered and the assumptions that lead to approximate conservation of momentum in a collision.