Q. A force $\left( 4\widehat{i} + \widehat{j} - 2\widehat{k} \right)N$ acting on a body maintains its velocity at $\left( 2\widehat{i} + 2\widehat{j} + 3\widehat{k} \right)ms^{- 1}$. The power exerted is
A) $4\ W$
B) $5\ W$
C) $2\ W$
D) $8\ W$
Explanation
(a) Here, Force, $\overrightarrow{F} = \left( 4\widehat{i} + \widehat{J} - 2\widehat{k} \right)N$
Velocity, $\overrightarrow{v} = \left( 2\widehat{i} + 2\widehat{j} + 3\widehat{k} \right)ms^{- 1}$
Power, $P = \overrightarrow{F}.\overrightarrow{v} = \left( 4\widehat{i} + \widehat{j} - 2\widehat{k} \right).(2\widehat{i} + 2\widehat{j} + 3\widehat{k})$
$= (8 + 2 - 6)\ W = 4W$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.