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A man throws balls with the same speed vertically upwards one after the other at an interval of 2 second. 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)1)More than 19.6 m/s2)At least 9.8 m/s3)Any speed less than 19.6 m/s4)Only with speed 19.6 m/s

A man throws balls with the same speed vertically upwards one after the other at an interval of 2 second. 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)1)More than 19.6 m/s2)At least 9.8 m/s3)Any speed less than 19.6 m/s4)Only with speed 19.6 m/s

Grade:12th pass

1 Answers

Eshan
askIITians Faculty 2095 Points
4 years ago
If there are to be atleast three balls in the sky at a time, it means that the first ball must have just reached the ground at the third throw. But the balls are thrown at an interval of 2 seconds.
Therefore the time of flight of the balls must be 2s+2s=4s.
\implies \dfrac{2u}{g}=4 \implies u=20m/s

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