Two Spacemen Are Floating Together with Zero Speed in a Gravity-Free

Multiple Choice

Two spacemen are floating together with zero speed in a gravity-free region of space. The mass of spaceman A is 120 kg and that of spaceman B is 90 kg. Spaceman A pushes B away from him with B attaining a final speed of 0.5 m/s. The final recoil speed of A is:

A) zero
B) 0.38 m/s
C) 0.5 m/s
D) 0.67 m/s
E) 1.0 m/s