Question

An astronaut of mass 82.2 kg is 31.2 m far out in space, with both the space ship and the astronaut at rest with respect to each other. Without a thruster, the only way to return to the ship is to throw his 0.502 kg wrench directly away from the ship. If he throws the wrench with a speed of 20.0 m/s, how many seconds does it take him to reach the ship?

Answer 1

0 =m1•v1 – m2•v2,
v1 =m2•v1/m1 =0.502•20/82.2 =0.122 m/s.
t = s/v1 =31.2/0.122 = 255.7 s =4.26 min