A 15 kg object and a 18 kg object are connected by a massless compressed spring and rest on a frictionless table. After the spring is
released, the object with the smaller mass has
a velocity of 12 m/s to the left.
What is the velocity of the object with the
larger mass?
Answer in units of m/s.

Hi there!

This is an example of a recoil collision.

Using the conservation of momentum:

The initial momentum is 0 kgm/s (objects start from rest), so:

We are given that the 15 kg block has a velocity of 12 m/s to the left, so:

Solve for v2':

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explanation: