Momentum and its Conservation

1. Jul 12, 2010

Mowgli

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

Astronaut Jane's lifeline to her spaceship comes loose and she finds herself stranded, "floating" 75.0m from the spaceship. She throws her 2.00kg wrench at 20.0m/s in a direction away from the ship. If she and her spacesuit have a combined mass of 175kg how long does it take her to coast back to the spaceship?

2. Relevant equations

3. The attempt at a solution

This one I am so lost about...

Do I use the equation: (Mass of Suit x Mass of Jane) Initial Velocity + Mass of wrench (Initial Velocity) = (M of Suit + M of Jane) (V 1 + M of wrench (V 1 of wrench)

Therefore = (175kg) 0 + 2kg (0) = (175kg) (final velocity + 2kg (20.0m/s)

2. Jul 12, 2010

bp_psy

All is good to this point.

3. Jul 12, 2010

Mowgli

Do I have to factor in the fact that she floated 75 m away?

4. Jul 12, 2010

bp_psy

That does not influence conservation of momentum.

You only need the distance to find the time it takes to get back to the ship.

5. Jul 12, 2010

Mowgli

then 0=175(final velocity) + 40

final velocity = -40/175
= -0.23 m/s ??

6. Jul 13, 2010

collinsmark

Looks okay so far.

7. Jul 13, 2010

Mowgli

what else needs to be done???

8. Jul 13, 2010

collinsmark

You need to find out how much time it takes for someone to travel 75.0 m when traveling at a speed of 0.229 m/s.