43. 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 ]

43. 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

Answer :  (b) More than 19.6 m/s

v = u + at

0 = u - 10(2)

u = 20 m/s 

therefore, more than 19.6 m/s