Laws Of Motion Question 265

Question: A ball of mass 400 gm is dropped from a height of 5m. A boy on the ground hits the ball vertically upwards with a bat with an average force of 100 newton so that it attains a vertical height of 20 m. The time for which the ball remains in contact with the bat is [g=10m/s2] [MP PMT 1999]

Options:

A) 0.12s

B) 0.08 s

C) 0.04 s

D) 12 s

Show Answer

Answer:

Correct Answer: A

Solution:

Velocity by which the ball hits the bat

v1=2gh1=2×10×5

or v1=+10m/s=10m/s

velocity of rebound v2=2gh2=2×10×20=20m/s or v2=20m/s

F=mdvdt=m(v2v1)dt=0.4(2010)dt=100N by solving dt=0.12sec



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