A) 4 N
B) 16 N
C) 20 N
D) 22 N
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 \[\Rightarrow -{{u}^{2}}=2\left( -10 \right)\times 2\Rightarrow {{u}^{2}}=40\] Again applying \[{{v}^{2}}-{{u}^{2}}=2aS\]for the upward journey of the ball, when the ball is in the hands of the thrower, \[{{v}^{2}}-{{u}^{2}}=2aS\] \[\Rightarrow 40-0=2\left( a \right)0.2\Rightarrow a=100m/{{s}^{2}}\] \[\therefore F=ma=0.2\times 100=20N\] \[\Rightarrow N-mg=20\Rightarrow N=20+2=22N\]
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