Determine the value of r in terms of l, k, and m for which the following function has a minimum.(adsbygoogle = window.adsbygoogle || []).push({});

V(r) = -(k/r) + (l^2/(2mr^2))

where l, k, and m are positive constants.

Prove that this is a minimum by showing that the second derivative of V(r) at the minimum is positive.

I have no idea how to even begin this...I am horrible at derivatives and am struggling in my physics class with them. Any help would be greatly appreciated.

I am then asked to derive Kepler's third law from Kepler's second law. So I feel I have a lot of work ahead of me.

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# Homework Help: Second derivative of effective potential

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