Question

A man throws balls with same speed vertically upwards one after the other at an refular interval of 2 sec. What should be the speed of throw so that more than two balls are in the sky at any time

Answer 1

HEY!!

✴For at least 3 balls to remain above the ground, the time of flight of the first ball must be more than or equal to 4 s.

✴Because in t = 4 s the third ball leaves the ground.

✴Now, for the first ball,

✔Initial velocity = u

✔Final velocity = -u

✔Acceleration = -g

✴So, -u = u – gt

▶ u = gt/2

▶u = 9.8 × 4/2

▶ u = 19.6 m/s

▶▶▶Thus, the ball must be thrown at speed more than or equal to 19.6 m/s.