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WeiLoong
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Homework Statement
A stationary object is released from a point P at distance 4R from the centre of the Earth which has radius R and mas M.What is the speed of the object when it hits the Earth's surfacehttps://scontent-kul1-1.xx.fbcdn.net/hphotos-xpt1/v/t34.0-12/11921921_10204785254702789_1979507807_n.jpg?oh=4a62967277ee876cb2de85befad6b89a&oe=55E68D61
Homework Equations
Gravitational
The Attempt at a Solution
By using the principle of conservational of energy.
1/2mv^2=-GMm/R-(-GMm/4R)
which is the final point-initial point
but the solution is
1/2mv^2=-GMm/4R-(-GMm/R)
which is the initial point-final point
So which 1 is correct i got little bit confused here.Arent we should use the final-initial to find the changes of gravitatinal potential energy?