A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by 2 ms−1and the boy changes his speed by 𝑥 = ms−1 , so that the kinetic energies of the boy and the man are again equal. Then 𝑥 in ms−1 is

May 10, 2022

by Ezee_Notes

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Physics Problems

Question: A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by 2 ms−1and the boy changes his speed by 𝑥 = ms−1 , so that the kinetic energies of the boy and the man are again equal. Then 𝑥 in ms−1 is

(A) $-2\sqrt{2}$

(B) $+2\sqrt{2}$

(D) 2

Answer: Option (B)

Solution:

A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by 2 ms−1and the boy changes his speed by 𝑥 = ms−1 , so that the kinetic energies of the boy and the man are again equal. Then 𝑥 in ms−1 is