Question

a man throws balls with the same speed vertically upward one after the other at an interval of 2seconds.What should be the speed of the throw so that more than two balls re in the sky at any time?

Answer 1

the first has to be above the ground when the second ball is thrown from the groundso the first ball has to be above from the ground for 2 seonds.s=ut-1/2*gt^2        t=2  and s=0 when first ball reaches the ground0= 2*u- 1/2*g*4u=g m/s        take g=9.8 m/s^2u= 9.8 m/s
speed has to be more than 9.8 m/s