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bcjochim07
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Homework Statement
Find the total gravitational potential energy of the three masses.
Homework Equations
U=-GMm/r
The Attempt at a Solution
U between the 10 kg mass & the 20kg mass
-(6.67*10^-11)(20kg)(10kg)/.20 m = -6.67 * 10 ^-8 J
U between the 20kg mass and the 5 kg mass
-(6.67*10^-11)(20kg)(5kg)/.10m = -6.67*10^-8 J
U between the 10 kg mass & the 5 kg mass
-(6.67*10^-11)(10kg)(5kg)/.2236 m = -1.49 * 10^-8 J
adding them up I got -1.483*10^-7 J
but the back of my book says -1.96 * 10^-7 J
Am I doing something wrong?