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

Answer 1

mV=m(-1/4 V)+MV'

1/2 mV^2=1/2m(V^2/16)+1/2MV'^2

form the first equation:
V'=mV(5/4)/M
Put that into the second equation for V', and solve for M

Answer 2

The guy in the top is right !

Answer 3

5/3m

Answer 4

It’s correct