Question

A ball is moving with speed of 6 m/s on horizontal surface falls in a vertical trench 4 m wide and 20 m deep. All collisions are elastic then $[g=10m/s^2]$

• A. Ball will come out of trench at A
• B. Ball will come out of trench at B
• C. Ball will hit wall B 3 time before coming out
• D. Ball will hit wall A 4 time before coming out

Answer 1

Answer: (A), (C)

The correct options are
A Ball will come out of trench at A
C Ball will hit wall B 3 time before coming out

As collision is elastic horizontal velocity is always 6 m/s.

Time of fall in trench $\Rightarrow 20=\frac{1}{2}\times 10\times t^2$
t = 2 sec
So total time taken by the ball to come back is 4 sec.

Horizontal distance covered in 4 sec is $d=6\times 4=24m$.
It will hit B 3 times and A 2 times before coming at A top.