Question

a boy in an open lift throws a ball up with a speed of 49m/s what will be time reqd for the ball to come back to the boy's hands when (a)the lift is stationary (b)the lift is moving up with 5 m/s

Answer 1

As long as velocity is constant, all frames of inertial reference are equal. This means that a & b will be one and the same answer. To get the answer, just solve for time in Vf=Vi+a*t to find the time required for the ball to reach the apex of the motion, then double to find the total elapsed time. Let me know if you find this helpful.

Answer 2

Ya, and the acceleration is always -9.8m/s^2 in the y coordinate.