Conservation of Momentum of astronaut

[jonnejon]

Homework Statement

An astronaut is a distance L from her spaceship, and is at rest with respect to the ship, when she discovers that her tether has broken. She tosses a wrench with a speed of V_W in the opposite direction of the ship to propel herself back to the ship. The astronaut has mass M_A, and the wrench has mass M_W.

How long does it take her to reach the ship in terms of L, M_A, M_W and V_W?

Homework Equations

Conservation of momentum: P_i=P_f
I don't know what equation to use to find time? v= d/t?

The Attempt at a Solution

(M_A+M_W)(V_i)=(M_W)(V_Wf)-(M_A)(V_Af)
V_Af=(M_f)(V_Wf)/(M_A)

t=d/v
t=(L)(M_A)/(M_W)(V_Wf)

Is that right? Thanks.

 

[Dr. Jekyll]

Seems correct to me.