Elastic collision between two bodies

1. The problem statement, all variables and given/known data
A body of mass 2.0Kg makes an elastic collision with another body at rest and continues to move in the original direction but with one-fourth of its original speed. What is the mass of the other body?

2. Relevant equations
Because it is an elastic collision I know that Energy and momentum are conserved.

So, m1v1i+ m2v2i = m1v1f+m2v2f

V1f = V2f = Vf

3. The attempt at a solution

I’m not really sure where to go because I’m not given the velocity of the second block after the collision.

2*v1i + 0 = 2*(1/4v1i) + m2v2

I’m confused because it states that the original block continues to move in the original direction. Because the blocks don’t adhere to each-other or go in opposite directions I’m not sure what to do.


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