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## Homework Statement

By use of the graph in part (a), calculate the gravitational field strength at a distance 2R from the centre of the Earth.

## Homework Equations

g = delta V / Delta r filed strength is the potential gradient

## The Attempt at a Solution

I have drawn the gradient on at 2r=R and calculated it. I have also done another at 3R to check what is confusing me.

I've just written out the equations; if V=GM/r and you divide that by r you get GM/r^2, which = g. So this must be valid for any point. In that case, why bother with the inaccuracy of drawing a tangent? Why not just read off the value of V at that value of r??

Any helpful pointers appreciated

D