A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by $2{\rm{\;m}}{{\rm{s}}^{ - 1}}$ and the boy changes his speed by $x = {\rm{m}}{{\rm{s}}^{ - 1}}$, so that the kinetic energies of the boy and the man are again equal. Then x in ${\rm{m}}{{\rm{s}}^{ - 1}}$ is

NEET UG PHYSICS MCQ: WORK-ENERGY-POWER

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A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by

2\mathrm{\;m}{\mathrm{s}^{ - 1}}

and the boy changes his speed by

x = \mathrm{m}{\mathrm{s}^{ - 1}}

, so that the kinetic energies of the boy and the man are again equal. Then x in

\mathrm{m}{\mathrm{s}^{ - 1}}

View answer and explanation

Correct option: B

+ 2\sqrt 2

Option B (

+2\sqrt 2

) is correct because it is the value of x that makes the kinetic energies of the man and boy equal after the speed changes.

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{A}

2 {~m}

\mathrm{\vec F} = - K\left( {y\hat i + x\hat j} \right)

\mathrm{\vec F}

9.8\;\mathrm{m}{\mathrm{s}^{ - 1}}

\mathrm{\vec F} = \left( {\hat i + 2\hat j + 3\hat k} \right)

{\mathrm{\vec r}_1} = \left( {\hat i + \hat j + \hat k} \right)

{\mathrm{\vec r}_2} = \left( {\hat i + \hat j + 2\hat k} \right)