# Outer space question

## Homework Statement

A 63 kg astronaut at rest in space throws a 10 kg oxygen tank with a speed of 12 m/s. What is the velocity of the astronaut immediately after throwing the tank?

Which formula would I use to solve this? Thanks in advance.

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nrqed
Homework Helper
Gold Member

## Homework Statement

A 63 kg astronaut at rest in space throws a 10 kg oxygen tank with a speed of 12 m/s. What is the velocity of the astronaut immediately after throwing the tank?

Which formula would I use to solve this? Thanks in advance.
Conservation of momentum. Here, the total momentum before was zero. so th etotal momentum after will be zero.

Yes, thats what i was thinking. thanks again.

I get .........120/63.

I get .........120/63.
oh really?

actually, its -1.9 m/s because the astronaut goes backwards.

Last edited:
cristo
Staff Emeritus
oh really?

actually, its -9.1 m/s because the astronaut goes backwards.
I think you may mean -1.9m/s

Haha, yeah ill change it.

oh really?

actually, its -9.1 m/s because the astronaut goes backwards.
Yes, and I actually chose the sign convention as such. Good lord trying to be helpful. And you'll notice, the question states the problems in terms of speed and asks for velocity. Either answer is correct.