Saturday, 11 July 2015

newtonian gravity - Signs in proof of gravitation potential energy (GPE)


Proof of gravitational potential energy.



Work done by gravity in bringing mass from infinity to a distance of $r$ between masses.


When we use the integration formula and arrive at the answer we get $-GMm/r$ taking lower limit as infinity and upper as $r$.


But this work should be positive as force and displacement are in same direction.


Please explain.


If my proof was wrong, then tell any other satisfying proof for GPE.




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