Laws Of Motion Question 322

Question: A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes up to 2 m height further, find the magnitude of the force. (Consider$ g=10m/s^{2} $ ).

Options:

A) 4 N

B) 16 N

C) 20 N

D) 22 N

Show Answer

Answer:

Correct Answer: D

Solution:

[d] Let the velocity of the ball just when it leaves the hand is u then applying ,

$ v^{2}-u^{2}=2aS $ For upward journey

$ \Rightarrow -u^{2}=2( -10 )\times 2\Rightarrow u^{2}=40 $

Again applying $ v^{2}-u^{2}=2aS $

for the upward journey of the ball, when the ball is in the hands of the thrower,

$ v^{2}-u^{2}=2aS $

$ \Rightarrow 40-0=2( a )0.2\Rightarrow a=100m/s^{2} $

$ \therefore F=ma=0.2\times 100=20N $

$ \Rightarrow N-mg=20\Rightarrow N=20+2=22N $



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