Homework Help: In deep space

1. May 12, 2010

bon

1. The problem statement, all variables and given/known data

cylindrical space station - large diameter, thin walled - radius r, mass M rotating in deep space, no gravity

1)radial spokes of negligible mass connect the cylinder ti the centre of motion. Astronaut mass m climbs a spoke to the centre. What is the fractional change in apparent gravity on the surface of the cylinder?

2)if the astronaut climbs halfway up a spoke and lets go, how far form the base of the spoke will he hit the cylinder? Assume the astronaut is point like..

2. Relevant equations

3. The attempt at a solution

1) Got the answer to be 1+m/M for ratio after/before..

is this right? I applied conservation of energy rather than angular momentum...why is angular momentum not conserved?

2) How do i do this one? Consv of energy again?

2. May 12, 2010

bon

anyone?

3. May 12, 2010

bon

what is conserved as the astronaut climbs down a spoke - angular momentum or total energy, and why?

4. May 12, 2010

diazona

What do you think? (and why?)

5. May 12, 2010

bon

My hunch is that angular momentum is conserved but not energy...because as he goes down the spoke there is no torque wrt centre of the cylinder..

but can't see why energy wouldn't be conserved..

6. May 12, 2010

diazona

Friction? Heat? Flexing of the space station? (not to mention the motion of the astronaut's body)

Your hunch is correct.

7. May 12, 2010

bon

Thanks okay so how do I solve part 2?

My attempt:

When he's half way up a spoke, I = Mr^2 + 1/4 mr^2

After he lets go I = Mr^2

angular mom is conserved again so Mr^2 w2 = (Mr^2 + 1/4mr^2)w1...

don't see how i can use this to work out how far from the base of the spoke he hits the cylinder!

8. May 12, 2010

bon

I don't think I even understand why he'd fall! I thought you only experienced the "apparent" gravity when you were on the inner surface of this rotating cylinder..

9. May 13, 2010

bon

so...?

10. May 13, 2010

bon

Sorry just thought I'd quote you to see if you can help with my next question... thanks

11. May 13, 2010

?????