Laws Of Motion Question 412
Question: If a man throws up a ball and catches it after some time, this time is called time of flight. Time of flight in these types of motion depend on whether the man is stationary or he is accelerated. If the man is in a moving lift throws a ball and catches it after time $ t _{1} $ when lift is moving up with acceleration a and catches the ball in time $ t _{2} $ if the lift is moving down with same acceleration a. The speed with which ball is thrown w.r.t. man -
Options:
A) $ \frac{gt _{1}t _{2}}{t _{1}-t _{2}} $
B) $ \frac{gt _{1}t _{2}}{t _{1}+t _{2}} $
C) $ \frac{2gt _{1}t _{2}}{t _{1}-t _{2}} $
D) $ \frac{2gt _{1}t _{2}}{t _{1}+t _{2}} $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ t _{1}=\frac{2u}{g+a} $ and $ t _{2}=\frac{2u}{g-a} $ Solving, $ u=\frac{gt _{1}t _{2}}{t _{1}+t _{2}} $
