A circular platform rotates around a vertical axis with angular velocity ω = 10 rad/s. On the platform is a ball of mass 1 kg, attached to the long axis of the platform by a thin rod of length 10 cm (α = 30°). Find normal force exerted by the ball on the platform (in newton). Friction is absent.

Question

G1 Physics · Accepted Answer

The ball moves in a horizontal circle of radius r=0.10cos30°. Required centripetal force is mω²r=1×100×0.10cos30°=5√3 N. If rod force is S along the rod, S cos30°=5√3 gives S=10 N. Its upward component is 5 N, so vertical balance N+5=10 gives N=5 N.