Gravitational potential question

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cata03
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#1
Report Thread starter 3 months ago
#1
I’m doing some AQA CPG practice questions (4.2 on the attached image) and I’m confused about this - I thought that electric potential energy was a scalar, so why have they taken one potential away from the other instead of adding them?
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Pangol
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#2
Report 3 months ago
#2
It does look like they've got this wrong.

4.1 gives the mass of planet 1 as 50M (and I can see that they use this in their solution to 4.2). So the gravitational potential at a distance of 3.10 x 1010 m from the centre of planet 1 is -G(50M)/(3.10 x 1010) = -GM/(6.20 x 108). This is bigger in magnitude than the value they give for the gravitational potential at the point between the two planets. It can't be easier to remove an object from this point to infinity because of the presence of planet 2, that can only make it harder to do so.

Unless we're both missing something (far from impossible in my case!), I agree with you.
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