A man throws balls with same speed vertically upwards one after the other at an interval of 2 s. What should be the speed of throw so that more than two balls are in the sky at any time?

Options

A. The vertical component of velocity of the shell just after it is fired is `55 m//s`, if the shell has to pass through the hoop a.
B. The shell will pass through both the hoops if `x=40 m`
C. The shell will pass through both the hoops if `x=20 m`
D. The vertical component of velocity of the shell just after it is fired is `45 m//s`, if the shell is to pass through both the hoops

Answer

A, B

Explanation

As given horizontal velocity `=40 m//s`
`u cos theta xxt=40, t=1` sec
at `t=1`, height `=50 m`
`:. 50=u sin theta xx1-1//2xxgxx1rArr u sin theta=55`
`:.` Initial vertical component `=u sin theta=55 m//s`
As hoop is on same height of the trajectory. So by symmetry x will be 40 m.