A block of mass m and charge q is released on a long smooth inclined plane magnetic field B is constant, uniform, horizontal and parallel to surface as shown. Find the time from start when block loses contact with the surface.

Question

G1 Physics · Accepted Answer

Motion down the smooth incline has v=g sinθ·t. Contact is lost when magnetic force qvB equals the normal component mg cosθ. Thus qB(g sinθ)t=mg cosθ, giving t=m cotθ/(qB). Hence C.