## Linear Momentum

How can we describe "the motion" of, say, a moving car? We have already described its motion in terms of the Kinetic Energy,

K = ( ^{1}/_{2}) m v^{2}

Anotherway to describe its motion is in terms of itsmomentum,Momentum= mass xvelocity

p= mvNotice tha

momentumis avector; there is adirectionto the momentum. That wasnottrue for Kinetic Energy.Newton's Second Law, which we have written as

F= macan also be written in terms of momentum,

F= ma= m (dv/dt) = d(mv)/dt = dp/dt

F= dp/dtThe force acting on an object equals the time rate of change of the momentum of that object.

ToCConservation of MomentumReturn to ToC, Ch9, Linear Momentum(c) Doug Davis, 2001; all rights reserved