A small block is shot into each of the four tracks as shown below. Each of the tracks rises to the same height. The speed with which the block enters the track is the same in all cases. At the highest point of the track, the normal reaction is maximum in :

Options

A.
B.
C.
D.

Answer

A

Explanation

Let .r. the radius of curvature of the track at the highest point then centripetal force `(mv^(2))/(r)=N+mg` (N = normal reaction)
or `N=(mv^(2))/(r)-mgorNprop(1)/(r)`
This means N will be maximum for the track having minimum radius of curvature.