Work (W) Problem

1. Feb 27, 2009

WolfpackPride

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

A crate with a mass of 120 kg glides through a space station with a speed of 2.5 m/s. An astronaut speeds it up by pushing on it from behind with a force of 250 N, continually pushing with this force through a distance of 5 m. The astronaut moves around to the front of the crate and slows the crate down by pushing backwards with a force of 220 N, backing up through a distance of 4 m.

What is the total amount of work done by the astronaut in these two maneuvers? (I correctly calculated this to be W = 370J)

After these two maneuvers, what is the speed of the crate?

2. Relevant equations

Kf - Ki = work

3. The attempt at a solution

I found the work, but need the speed. I just can't figure out how to pull the velocity out of that correctly

2. Feb 27, 2009

LowlyPion

If you want speed then what was the KE of the object initially?

How much net work did the astroworker do? If you add that to the object's energy, that's the final KE and Ke = ½mv²