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# Gravitational potential and Gravitational potential Energy – A doubt

I am very confused with the difference between U=GM/r which has a unit J/kg and U=GMm/r which is work done and have a unit of Joules. What are exactly their differences?

There’s a question “The gravitational potential difference between two points is 3.0×10^3 J/kg. Calculate the work done in moving mass of 4.0 kg between the two points.”

What I did was seeing their units and then equate since they’re J/kg and kg, I multiplied both magnitude which will give me ‘Joules’ in the end.

Like 3.0×10^3 J/kg = Workdone/4.0 kg

Please help, my print out book has some missing pages, which didn’t allow me to see the answer at the back of the book.

Posted by Taffs

Gravitational potential difference is the work done per unit mass in carrying a body from one place to other.

Work done has the unit J and therefore the potential difference (i.e the work done per unit mass) should have the unit J/kg

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