# Astronaut calculation help

1. Nov 16, 2006

### sunbunny

I have no idea how to start this problem:

An 80.0 spacewalking astronaut pushes off a 620 satellite, exerting a 100 force for the 0.590 it takes him to straighten his arms.How far apart are the astronaut and the satellite after 1.20 ?

I know that it involves Newton's 3rd law since the astronaut is applying a force onto the satellite and in turn the satellite pushes back on the astronaut to cause him to move but other that that I'm confused how to solve this problem. If anyone can give me some feedback that would be great!

Thanks

2. Nov 16, 2006

### Staff: Mentor

First, you *must* include units with all of the numbers you list. They are meaningless otherwise.

Next, use conservation of energy to solve it. What work does the astronaut perform in the push? How does that convert into KE? And remember that conservation of momentum will also factor in.

3. Nov 16, 2006

### Hootenanny

Staff Emeritus
Your are correct, Newton's third law is crucial here, but one must also consider Newton's second law, or more specifically the impulse-momentum theorem.

Edit: Berkeman got there first Is the 0.590 a distance or a time period?

4. Nov 16, 2006

### sunbunny

sorry about forgetting the units.
An 80.0 kg spacewalking astronaut pushes off a 620kg satellite, exerting a 100N force for the 0.590s it takes him to straighten his arms.How far apart are the astronaut and the satellite after 1.20s ?

5. Nov 16, 2006

### Staff: Mentor

So now go ahead and use the work/KE/momentum stuff and Hootenanny's suggestion. Show your work -- what answer do you get?