I watched the "Helping Hand" episode of Love, Death & Robots on NetFlix, where the protagonist is adrift in space. Every second she is further from her ship, and when her tank is out of oxygen, she throws her glove to propel herself back to the ship.
But I don't know how propulsion works in zero gravity. She needs to throw something heavy to make this propulsion? If she throws something like her watch, will it have the same effect as if she throws her heavy suit gloves?
My question is, if you are in space, and you needs to change velocity, and you have something to throw, is it better to throw the heaviest thing?
Best Answer
Yes. For two reasons.
When you throw something, there is a force exerted on you just like you exert a force on the object you throw. Momentum is conserved, so whatever momentum you give to the object you throw in one direction, you gain from the object in the opposite direction.
The first reason you want to throw something heavier is that when you apply a force on a heavier object, it won't have as much of an acceleration as a lighter object. Thus, you can push with the same force that you'd push a lighter object with, but for longer, since the object won't fly away immediately. And since you applied the same force but for a longer period of time, you'll have delivered more momentum to object you pushed, and will have gained more momentum in the opposite direction.
(When in trouble, think of the extremes - a person throwing their watch versus pushing off a massive wall)
The second reason you want to throw something heavier is that the lighter you are, the faster your velocity will be with the momentum gained opposite to the direction you threw the object. By getting rid of heavier things you're carrying, it'll be easier to accelerate with any amount of force applied - you'll have a higher velocity with any momentum you gain.