Question

a motor cyclst rides an a vertical circle of redius 3m find minimum speed required so that he does not lose contact with the sphere at the high point

Answer 1

at the top of the sphere gravitational force is downward ...
and the condition for not to lose the contact will be
$\frac{m {v}^{2} }{r} > mg \\ v > \sqrt{rg} \\ v > \sqrt{3 \times 10} \\ v > \sqrt{30}$