A charged particle of mass m and charge -q is released from rest in the shown track. At point P, normal reactions with and without a uniform horizontal magnetic field are N₁ and N₂. If N₁-N₂=5Bq√(gR)/k, find k.

Question

G1 Physics · Accepted Answer

At P the speed follows from energy conservation, and the magnetic force changes only the normal equation. The reaction difference equals qvB. Using the speed at P from the shown height gives N₁-N₂=Bq√(5gR), which compared with 5Bq√(gR)/k gives k=5.