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## Homework Statement

A 1600 kg object is initially at rest 400 km above the earth’s surface. The object falls straight

down and generates 8.3x10^8J of heat energy while descending to an altitude of 100 km.

What is the velocity of the object at this altitude?

(http://i1070.photobucket.com/albums/u488/ScatlettArmadillo/Question20.jpg)

## Homework Equations

Ek = (mv^2)/2

Ep = -GMm/r

G=6.67^-11

Mass of Earth = 5.98x10^24 kg

Radius of Earth = 6380000 m

Force of Gravity = GMm/r^2

## The Attempt at a Solution

http://i1070.photobucket.com/albums/u488/ScatlettArmadillo/Question20-1.jpg

Once I got to the final step I had to find the root of a negative, which is not possible, so I must have made an error somewhere else, but I can't seem to work out where.

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