A boy is rolling a 0.5, kg ball on the fricti | vedclass

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Question

Given, $m =0.5 kg$ and $u =20 m / s$

Initial kinetic energy $\left( k _{ i }ight)=\frac{1}{2} mu ^{2}$

$=\frac{1}{2} 	imes 0.5 	imes 20 	im

Vedclass · Accepted Answer

$4.47$

Vedclass · Answer

Given, $m =0.5 kg$ and $u =20 m / s$

Initial kinetic energy $\left( k _{ i }ight)=\frac{1}{2} mu ^{2}$

$=\frac{1}{2} 	imes 0.5 	imes 20 	imes 20=100 J$

After deflection it moves with $5 \%$ of $k _{ i }$

$	herefore k _{ f }=\frac{5}{100} 	imes k _{ i } \Rightarrow \frac{5}{100} 	imes 100$

$\Rightarrow k_{ f }=5 J$

Now, let the final speed be 'v' $m / s$, then :

$k_{ f }=5=\frac{1}{2} mv ^{2}$

$\Rightarrow v ^{2}=20$

$\Rightarrow v =\sqrt{20}=4.47 m / s$

A boy is rolling a $0.5\, kg$ ball on the frictionless floor with the speed of $20\, ms ^{-1}$. The ball gets deflected by an obstacle on the way. After deflection it moves with $5 \%$ of its initial kinetic energy. What is the speed of the ball now ? (in $ms ^{-1}$)

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