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

Options

A. only with speed 19.6m/s
B. more than 19.6m/s
C. at least 9.8m/s
D. any speed less than 19.6m/s

Answer

B

Explanation

Height attained by ball in 2 seconds `= (1)/(2) (9.8) xx 2^(2) = 19.6m`
The same distance will be covered in 2 second (for descent). Time interval of throwing balls, remains same. So, for two balls remaining in the air, the time of ascent or descent must be greater than 2 second. This is achieved only at speed more than 19.6 m/sec