(B) Given: Mass $m = 0.5\, kg$,Initial speed $u = 20\, ms^{-1}$.Initial kinetic energy $K_i = \frac{1}{2} mu^2 = \frac{1}{2} \times 0.5 \times (20)^2

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(B) Given: Mass $m = 0.5\, kg$,Initial speed $u = 20\, ms^{-1}$.Initial kinetic energy $K_i = \frac{1}{2} mu^2 = \frac{1}{2} \times 0.5 \times (20)^2 = 100\, J$.After deflection,the final kinetic energy $K_f$ is $5\%$ of $K_i$.$K_f = \frac{5}{100} \times 100 = 5\, J$.Let the final speed be $v$. Then $K_f = \frac{1}{2} mv^2$.$5 = \frac{1}{2} \times 0.5 \times v^2$.$5 = 0.25 \times v^2$.$v^2 = \frac{5}{0.25} = 20$.$v = \sqrt{20} \approx 4.47\, ms^{-1}$.

Class 11 Physics Work, Energy, Power and Collision Kinetic Energy

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$A$ boy is rolling a $0.5\, kg$ ball on a frictionless floor with a 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 $ms^{-1}$)

JEE MAIN 2021 All JEE MAIN

A
$19.0$
B
$4.47$
C
$14.41$
D
$1.00$

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Work, Energy, Power and Collision

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Kinetic Energy

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$A$ boy is rolling a $0.5\, kg$ ball on a frictionless floor with a 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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