Question

a helicopter is going vertically upward with a velocity of 20m/s, when it is 60m above the ground, a stone is gently released from it, the time taken by the stone to reach the ground is ______

Answer 1

Answer:

6 seconds

Explanation:

It is like a stone is thrown upwards from a height of 60m with a velocity of 20m/s . This is because when ab object is released from an another moving body, it carries it's "velocity" and not the acceleration. As soon as the stone is released from the helicopter , it attains the velocity 20m/s and acceleration due to gravity.

Now,

Time taken to reach highest point = u/g = 20/10 = 2s..***

height till the highest pt = u^2/2g = 400/20 = 20m

Now, H= 20+60= 80m

From the highest point,

T = √(2H/g)

=√{2(80)/10}

=√16 = 4s...****

FROM *** AND ****

total time taken = 4+2= 6s (ANS)