A motorcycle rider moves in a horizontal circle on the inner vertical wall of a cylindrical Well of Death of radius 5 m. The coefficient of friction between tyres and wall is 0.5. Take g = 10 m/s². If the minimum speed required is N m/s, find N.
Physics · Circular Motion · friction and circular motion
JEE Mains NEET JEE Advanced

Question

A motorcycle rider moves in a horizontal circle on the inner vertical wall of a cylindrical Well of Death of radius 5 m. The coefficient of friction between tyres and wall is 0.5. Take g = 10 m/s². If the minimum speed required is N m/s, find N.

Physics · Circular Motion · friction and circular motion

G1 Physics · Accepted Answer

The normal reaction of the wall provides centripetal force: N_R = mv²/r. To prevent downward slipping, upward static friction must balance weight. At the limiting minimum speed, μN_R = mg. Thus μ(mv_min²/r) = mg, so v_min² = rg/μ = 5×10/0.5 = 100. Hence v_min = 10 m/s and N = 10.