Given, m=0.5kg and u=20ms−1
Initial kinetic energy (ki)=21mu2
=21×0.5×20×20=100J
After deflection it moves with 5 of ki
∴kf=1005×ki⇒1005×100
⇒kf=5J
Now, let the final speed be ′v′ms−1, then:
kf=5=21mv2
⇒v2=20
⇒v=20=4.47ms−1
JEE Main 2021 — Physics Mechanics
A boy is rolling a 0.5kg ball on the frictionless floor with the speed of 20ms−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?
Held on 17 Mar 2021 · Verified 6 Jul 2026.
19.0ms−1
4.4ms−1
14.41ms−1
1.00ms−1
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