Work done to reach the point where the gravitational potential is zero

[Bolter]

Homework Statement

Calculate the work done on the mass to a point where the gravitational potential is zero

Relevant Equations

V = –GM/r

Hi there

I have been attempting the parts to this question and I'm finding some trouble on how to answer the last part which is d)iii

Here is what I have done for the rest of the parts and what I think I should start off with in part d)iii

Thanks!

 

[gneill]

Gravitational potential represents the work done (per kg) in order to bring the object from infinity to its current location.

By symmetry, the work to send the object back to infinity must be the same but of opposite sign.

 

[Bolter]

Gravitational potential represents the work done (per kg) in order to bring the object from infinity to its current location.

View attachment 256044

By symmetry, the work to send the object back to infinity must be the same but of opposite sign.

I see, this is what I have tried now

Where I assumed that the current location of the 5 kg mass was lying at the surface of the Earth so the distance r was the radius of the Earth then

 

[gneill]

Given your assumption that looks good.