question_answer

A stone is projected from a horizontal plane. It attains maximum height '\[H\]' and strikes a stationary smooth wall and falls on the ground vertically below the maximum height. Assuming the collision to be elastic the height of the point on the wall where ball will strike is

A) \[\frac{H}{2}\]             

B) \[\frac{H}{4}\]

C) \[\frac{3H}{4}\]                       

D) None of these

Correct Answer: C

Solution :

[c] \[H=\frac{1}{2}g{{(2t)}^{2}}=2g{{t}^{2}}\]                ...(1) \[h=H-\frac{1}{2}g{{t}^{2}}\]                                   ...(2) Solving eqns (1) and (2), we get \[h=H-\frac{H}{4}=\frac{3H}{4}\]