An open lift is coming down from the top of a building
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An open lift is coming down from the top of a building at a constant speed v=10 m/s. A boy standing on the lift throw a stone vertically upwards at a speed of 30 m/s w.r.t. himself. The time after which he will catch the stone is:
A.
8 sec
B.
10 sec
C.
4 sec
D.
6 sec
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
0=30t+12(−10)t2⇒t=0 or 6
∴ time taken by the ball to return to boy is 6 seconds.