**Moving Target**

Now that we have examined the elastic collision of a projectile and a stationary target, let us examine the situation in which both bodies are moving before they undergo an elastic collision.

Note that the assignment of subscripts 1 and 2 to the bodies is arbitrary. If we exchange those subscripts in, we end up with the same set of equations. Note also that if we set V2i = 0, body 2 becomes a stationary target .

CHECKPOINT4: What is the final linear momentum of the target in the initial linear momentum of the projectile is 6 kg . m/s and the final linear mo en tum of the projectile is (a) 2 kg· m/s and (b) -2 kg· m/s? (c) What is the final kinetic energy of the target if the initial and final kinetic energies of the projectile are, respectively.

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