Laws Of Motion Question 269

Question: A solid disc of mass M is just held in air horizontally by throwing 40 stones per sec vertically upwards to strike the disc each with a velocity 6 ms1 . If the mass of each stone is 0.05kg what is the mass of the disc(g=10ms2 ) [Kerala (Engg.) 2001]

Options:

A) 1.2kg

B) 0.5kg

C) 20kg

D) 3kg

Show Answer

Answer:

Correct Answer: A

Solution:

Weight of the disc will be balanced by the force applied by the bullet on the disc in vertically upward direction. F=nmv=40×0.05×6=Mg

therefore M=40×0.05×610=1.2kg



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