A small block is shot into each of the four track as shown in Fig 15.7.1. Each of the track 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. (a)
B. (b)
C. (c)
D. (d)

Answer

A

Explanation

Since the body presses the surface with a force N, according to Newton's third law the surface presses the body with a force N. The other force acting on the body is its weight `mg`.

For circular motion to take place, a centripetal force is required which is provided by `mg+N`.
`:. mg+N=(mv^2)/(r)`
If the surface is smooth, then on applying conservation of mechanical energy, the velocity of the body is always same at the topmost point. Hence, N and r have inverse relationship. From the figure it is clear that r is minimum for first figure, therefore, N will be maximum.