Question

An astronaut with a mass of `90 kg` is floating in space. If the astronaut throws a `20 kg` object at a speed of `5 m/s`, how much will his speed change by?

Answer 1

I found: `v=-1.11m/s` (in the opposite direction)

Explanation:

We can use conservation of momentum where momentum is `p=mv` (in one direction only) and the momentum (astronaut mass M+object mass m) before will be equal the momentum after.
We can write:
`(M+m)v=Mv+m"u`
`(90+20)*0=90*v+20*5`
`0=90v+100`
so `v=-100/90=-1.11m/s` (in the opposite direction)