Question

A man throws ball with the same speed vertically upwards one after the other at an interval of 2 seconds. What should be the speed of the throw so that more than two balls are in the sky at any time ? $(Giveng=9.8m/s^2)$

• A. More than $19.6m/s$
• B. At least $9.8m/s$
• C. Any speed less than $19.6m/s$
• D. Only with speed $19.6m/s$

Answer 1

Answer: (A)

More than $19.6m/s$

The correct option is A.

We have $t=2s$

When the ball is thrown upward the final velocity become zero.

Therefore,

$v=u+at$

$0=u-gt$

Here, g is acceleration due to gravity

$u=gt$

$=9.8\times 2=19.6$ m/s

Thus, when he throws a ball with a minimum speed of 19.6m/s in a time interval of 2s.

Then two balls can be in the air simultaneously.