You may have seen in a circus a motorcyclist driving in vertical loops inside a death well (a hollow spherical chamber with holes so the spectators can watch from outside) Explain clearly why the motorcyclist does not drop down when he is at the uppermost point of death well with no support from below What is the minimum speed required at the uppermost position to perfrom a vertical loop if the radius of the chamber is 25 m ?

Explanation

At the uppermost point `N + mg = (mv^2)/( R)` , where N is the normal force (downwards) on the motorcyclist by the ceiling of the chamber. The minimum possible speed at the uppermost point corresponds to N = 0.
`i.e. v_("min") = sqrt(R_g) = sqrt(25 xx 10) = 16 ms^(-1)`