1. The problem statement, all variables and given/known data Angular momentum of a particle is: L = (dr/dt) x mr Show that (dL/dt) = (d2r/dt2) x mr 2. Relevant equations ----- 3. The attempt at a solution My atempt is that I tried writing it in the form y = mx + c but I don't think that would be relevant. Next I tried straight forward rule application derivision (it was wrong to try that) Basically, my knowledge on differentiation isn't up to par and so far I haven't tried integrating it but I seriously doubt it'd lead to the answer and I don't know how to apply an intergral of (dL/dt) to the mr term. Thanks in advance I've also considered writing r = irx + iry + irz but again, no idea how to apply it in equation.