Kinematics Question 196

Question: A man in a balloon r it’sing vertically with an acceleration of 4.9m/sec2 releases a ball 2 sec after the balloon it’s let go from the ground. The greatest height above the ground reached by the ball is (g=9.8m/sec2) [MNR 1986]

Options:

A) 14.7 m

B) 19.6 m

C) 9.8 m

D) 24.5 m

Show Answer

Answer:

Correct Answer: A

Solution:

Height travelled by ball (with balloon) in 2 sec h1=12a t2=12×4.9×22=9.8 m

Velocity of the balloon after 2 sec v=a t=4.9×2=9.8 m/s

Now if the ball is released from the balloon then it acquire same velocity in upward direction.

Let it move up to maximum height h2

v2=u22gh2

therefore 0=(9.8)22×(9.8)×h2
h2 =4.9m

Greatest height above the ground reached by the ball =h1+h2=9.8+4.9=14.7 m



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