. A man throws the ball 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: More than 19.6 m/s
B: At least 9.8 m/s
C: Any speed less than 19.6 m/s
D: Only with speed 19.6 m/s
Given:t =2s ;g =9.8 m/s2
When the ball is thrown upward the final velocity become zero.i.e v =0
Now, Time taken by ball to reach maximum height
v =u - gt
O =u - gt
u = gt
On substituting the given, we get
u = 19.6 m/s
As a result, when he throws a ball at a minimum speed of in19.6 m/s a 2s time period, two balls can be in the air at the same moment.
The correct answer is A i.e More than 19.6 m/s.