Question

A space walking astronaut has become detached from her spaceship. She’s floating in space while holding nothing but a wrench. She is thinking about how to get back to the spaceship, which she can see 50m from her current location. What can she do to get back to the spaceship? Explain your answer using Newton's Laws of Motion.

Answer 1

Answer: The astronaut should throw the wrench in the direction opposite to the spaceship.

Explanation:

The basis for the answer is provided by the Newton's First Law of motion and, by implication, the Conservation of Momentum. In an inertial system, the sum of momenta of its parts remains constant. The astronaut with the wrench (inertial system) is assumed to be at a fixed position relative to the spaceship ("floating"). The astronaut needs to gain a positive velocity (and momentum) pointing to the ship. Momentum = (mass)x(velocity). By ejecting the wrench with a velocity (and momentum) in the direction away from the ship, the astronaut induces the desired momentum counteracting that of the wrench. The resulting speed depends on the mass of the astronaut as well as the mass and speed of the wrench, however, rest assured the astronaut will make it back to the ship at some point.