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 $
