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JEE Main Physics question

PhysicsWork, Energy and PowerJEE Main

A running man has the same kinetic energy as that of a boy of half his mass. The man speeds up by 2 ms⁻¹ and 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

Answer: (A)

Solution

Let man's mass M, boy's mass M/2, with initial speeds and . Equal KE: ½² = ½(M/² ⟹ = √2·. After the change: ½+2)² = ½(M/+x)² ⟹ √+2) = +x =

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Question ID VK-153567