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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?
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