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## Homework Statement

An astronaut lands on a new planet of radius R=3000km, and wants to measure its density. In order to do that, he drops a stone of unknown mass from the top of the space shuttle, which has a height of 92.5m and measures the time it takes it to reach the ground. t= 5s.

What is the density of the planet?

## Homework Equations

K=.5mv

^{2}

DeltaV= -GMm/Rf - (-GMm/Ri) where Rf and Ri are the radius of the planet and the radius of the planet + rocket height respectively.

K=delta V

## The Attempt at a Solution

I attempted to solve for the acceleration via kinematics.

I used .5at

^{2}=dY and found

a=2.72 m/s

^{2}.

Next, I calculated the final velocity using

vf

^{2}=sqrt(2adY)=22.433m/s.

I then proceeded to use my Energy equations in order to isolate big M. Unfortunately, my answer is negative and doesn't make sense.. Ehh, actually, the magnitude of it is within reason, but it being negative is what is getting me

answer= -3.77*10^23.. I don't think units cancel properly with what I did :/. Can anyone give me a pointer? I can do the rest if I can just calculate this mass.