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

A 2700 kg spacecraft is in a circular orbit 1000 km above the surface of Mars. How much work must the spacecraft engines perform to move the spacecraft to a circular orbit that is 4000 km above the surface?

mars: Mass=6.4185*10^23 KG, radius=3397000 m

**2. Relevant equations**

TME=U+KE

U=Gm1m2/R

KE=.5Gm1m2/r (this doesn't seem right for some reason)

**3. The attempt at a solution**

U1+k1+work=U2+k2

work=U2+k2-(u1+k1)

u1=2.630*10^10

ke1=1.315*10^10

U2=2.891*10^10

Ke2=1.446*10^10

TME1=3.945*10^10

TME2=4.337*10^10

Work= TME2-TME1=3.92*10^9

webassign says I'm wrong. Is my equation for either KE or potential energy incorrrect? Any help is appreciated.