Q. Consider a rubber ball freely falling from a height $h = 4.9\ m$ onto a horizontal elastic plate. Assume that the duration of collision is negligible and the collision with the plate is totally elastic. Then the velocity as a function of time will be
A) [image:3_image87.emf]
B) [image:3_image88.emf]
C) [image:3_image89.emf]
D) [image:3_image90.emf]
Explanation
(c) $h = \frac{1}{2}gt^{2},\ $(parabolic)
$v = - gt$and after the collision, $v = gt$ (straight line)
Collision is perfectly elastic then ball reaches to same height again and again with same velocity
[image:3_image190.emf]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.