Work Energy Power

JEE Main level, single correct, medium

115 of 183

Question 115 of 183

A particle which is experiencing a force, given by F⃗=3i^−12j^\vec{F}=3\hat{i}-12\hat{j}, undergoes a displacement of d⃗=4i^\vec{d}=4\hat{i}. If the particle had a kinetic energy of 3J3J at the beginning of the displacement, what is its kinetic energy at the end of the displacement?

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Answer: (B) 15J15J.

Work done by the force,F⃗.s⃗=(3i^+12j^)⋅(4i^)=12J\vec{F}.\vec{s}=\left(3\hat{i}+12\hat{j}\right)\cdot \left(4\hat{i}\right) =12J

By work energy theorem, Wtotal=∆K{W}_{total}=∆K

12J=Kf−Ki12+Ki=Kf12J={K}_{f}-{K}_{i} 12+{K}_{i}={K}_{f}

∴Kf=12+3=15J∴{K}_{f}=12+3=15J

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