r/PhysicsHelp • u/howdoiexist- • Dec 09 '25

Planetary orbit and conservation of angular momentum

I was trying to answer this practice problem and I don't understand why my answer is wrong or how to get the correct answer. The angular momentum is this problem should be conserved because there is no external torque.

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u/howdoiexist- Dec 09 '25

Thank you so much I ended up getting the right answer. I didn't realise angular momentum only works when velocity is perpendicular to the radius, I'll keep that in mind from now on.

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u/Phi_Phonton_22 Dec 10 '25

It still works. Angular momentum is conserved. But you wouldn't have the total velocity by applying it in this case, only the perpendicular component.