Q. A small block is shot into each of the four tracks as shown below. Each of the frictionless track rises to the same height. The speed, which the block enters the tracks, is same in all cases. At the highest point of the track, normal reaction is maximum in
A) [image:4_image37.jpeg]
B) [image:4_image38.jpeg]
C) [image:4_image39.jpeg]
D) [image:4_image40.jpeg]
Explanation
(a) Since the block rises to the same heights in all the four cases, from conversation of energy, speed of the block at highest point will be same in all four cases. Say it is $v_{0}$. Equation of motion will be
[image:4_image127.emf]
$N + mg = \frac{{mv}_{0}^{2}}{R}$
$or\ \ N = \frac{{mv}_{0}^{2}}{R} - mg$
R (the radius of curvature) in first case minimum. Therefore, normal reaction N will be maximum in first case.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.