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A man throws balls 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? [Given g = 9.8 m/s 2 ] (a) Only with speed 19.6 m/s (b) More than 19.6 m/s (c) At least 9.8 m/s (d) Any speed less than 19.6 m/s



A man throws balls 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? [Given g = 9.8 m/s2]


(a)    Only with speed 19.6 m/s


(b)    More than 19.6 m/s


(c)    At least 9.8 m/s


(d)    Any speed less than 19.6 m/s


 


Grade:10

1 Answers

Jitender Pal
askIITians Faculty 365 Points
10 years ago

(b)

Height attained by ball in 2 second =  × (9.8) × 22 = 19.6m

The same distance will be covered in 2 seconds, (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 seconds. This is achieved only at speed more than 19.6 m/sec.

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