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A man throws balls with the same speed v...

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 than two balls are in the sky at any time ? (Take `g = 9.8 m//s^(2)`)

A

at least 0.8 m/s

B

any speed less than 20 m/s

C

only with speed 20 m/s

D

more than 20 m/s

Text Solution

Verified by Experts

The correct Answer is:
D
Interval of ball throw`=2` sec.
If we want that minimum three (more than two) balls remains in air then time of flight of first ball must be greater than 4 sec.
`Tgt4` sec
`(2u)/(g)gt4` sec `impliesugt20(m)/(s)`
for `u=20(m)/(s)`. First ball will just strike the ground (in sky) second ball will be at highest point (in sky)
Third ball will be at point of projection or at ground (not in sky)
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