I'm confused by angular momentum. For a circle it's L = mvr so it seems that a 1kg mass travelling at 1 m/s at the edge of a circle 1 meter in radius would give L = 1 kg m^2/s whereas if it where at the edge of a cirle 2 meters in radius it'd have an angular momentum of 2 kg m^2/s. My problem is that I thought angular momentum was conserved as the radius changed so I'm wrong somewhere! Can someone please explain were my thinking is failing. Thanks.

Question

anonymous · Answer

My problem is that I thought angular momentum was conserved as the radius changed...
yes...if there is no external torque then L will be conserved...

anonymous · Answer

as you r saying if radius changes from 1 to 2m then L gets doubled ...but something is missing here...v will become half.

anonymous · Answer

Thanks. I understand now - v changes to keep angular momentum the same. I was stupidly keeping mv constant in my head.