## Conservation of Momentum

Consider two objects that "interact" or collide or have some effect on each other:

From Newton's Third Law of motion, we know

F_{12}= -F_{21}In terms of momentum, this means

F_{12}= dp_{1}/dt

F_{21}= dp_{2}/dtso that

d p_{1}/dt = - dp_{2}/dtor

d p_{1}/dt + dp_{2}/dt = 0d (

p_{1}+p_{2}) /dt = 0d

p_{Tot}/dt = 0where

p_{Tot}=p_{1}+p_{2}That is, the

total momentumof the system remainsconstant. This isConservation of MomentumConservation of Momentum is essentially a restatement of Newton's Third Law of Motion.

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