Conservation of Momentum in Collisions

You should now have concluded that momentum is conserved in all interactions.  But why is this so?

First, you should recognize that Newton’s Third Law still applies. When two objects interact, there is a Newton’s Third Law force pair acting between them. The forces are equal in magnitude and opposite in direction, and act for the same amount of time.

F₁ = -F₂ and t = t

F₁t = -F₂t and J₁ = J₂

This means that the impulse on the two objects will be equal in magnitude and opposite in direction.

Equal and opposite impulse means equal and opposite change in momentum. The momentum gained by one object will equal the momentum lost by the other. Since the total change in momentum equals zero, momentum is conserved. This can be rearranged to show that the total change in momentum equals zero, or momentum is conserved.

Momentum in Collisions

Now that you have explored collisions, develop an understanding of how conservation of momentum is applied to collisions. Try to answer the practice problems on your own prior to viewing the solutions. Click the player to begin.

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