a very large umber of balls are thrown vertically upwards in quick succession in such a way that the next ball is thrown when the previous one at maximum height. If the maximum height is 5m the number of balls thrown per minute is????

Max. Height reached by each ball (h) = 5 m.

Final velocity, v =0

Let Initial velocity=u m/s

=> v^2 = u^2 - 2gh

=> 0=u^2 - 2×10×5

=> u^2 = 100

=> u = 10 m/s

Now, put u=10 in first equation of motion to get the value of time,

V = u - gt

=>0 = 10 -10t

=> t= 1 sec.

Time taken by each ball to reach the max. height = 1 sec.

Conversely,

No. of balls thrown in 1 sec. = 1

No. of balls thrown in 1 min. or 60 sec. =60 balls.