Question

Two balls collide head-on on a table. The first ball has a mass of 0.50 kg and an initial velocity of 12.0 m/s. The second ball has a mass of 0.75 kg and an initial velocity of -16.0 m/s. After the collision, the first ball travels at a velocity of -21.6 m/s. What is the velocity of the second ball after the collision? Assume a perfectly elastic collision and no friction between the balls and the table.
A. 6.4 m/s
B. 11.3 m/s
C. 17.8 m/s
D. 21.6 m/s

Answer 1

A is correct according to below calculation.
m₁v₀₁+m₂v₀₂=m₁v₁+m₂v₂
((m₁v₀₁+m₂v₀₂)-m₁v₁)/m₂=v₂
v₂=((.5*12-.75*16)+(.5*21.6))/.75
v₂=6.4 m/s