While in Earth's orbit, an 80-kg astronaut carrying a 20-kg tool kit is initially drifting toward a stationary (relative to her) space shuttle at a speed of 2 m/s. If she throws the tool kit toward the shuttle with a speed of 6 m/s as seen from the shuttle, her final speed is
A)1 m/s toward the shuttle.
B)1 m/s away from the shuttle.
C)2 m/s toward the shuttle.
D)4 m/s toward the shuttle.
E)6 m/s away from the shuttle.

Question

Quizplus · Accepted Answer

Using conservation of momentum, the initial momentum of the system (astronaut + tool kit) is equal to the final momentum. Initially, the total momentum is (80 kg + 20 kg) * 2 m/s = 200 kg*m/s. After throwing the tool kit, the momentum is 20 kg * 6 m/s + 80 kg * v = 200 kg*m/s. Solving for v gives v = 1 m/s toward the shuttle.

While in Earth's Orbit, an 80-Kg Astronaut Carrying a 20-Kg