Non-elastic collision without outside influence

[nhmockus]

A ball A of mass makes a head-on elastic collision with a second ball B (at rest) and rebounds in the opposite direction with a speed equal to one-fourth its original speed. What is the mass of the second ball B?

I think an appropriate equation for this is v(1)= u(1)*(m(1)-m(2))/(m(1)+m(2))

I tried solving this by changing v(1) to 1/4 u(1) and then trying to find something that makes that long equation next to u(1) equal 1/4 but I can't seem to find anything

 

[gneill]

A ball A of mass makes a head-on elastic collision with a second ball B (at rest) and rebounds in the opposite direction with a speed equal to one-fourth its original speed. What is the mass of the second ball B?

I think an appropriate equation for this is v(1)= u(1)*(m(1)-m(2))/(m(1)+m(2))

I tried solving this by changing v(1) to 1/4 u(1) and then trying to find something that makes that long equation next to u(1) equal 1/4 but I can't seem to find anything

Hi nhmockus, welcome to Physics Forums.

Remember that velocities have directions.