Question

A force $(4\hat{i}+\hat{j}-2\hat{k})N$ acting on a body maintains its velocity at $(2\hat{i}+2\hat{j}+3\hat{k})m{s}^{-1}$. The power exerted is:

• A. $4W$
• B. $5W$
• C. $2W$
• D. $8W$

Answer 1

The correct option is A $4W$

Force, $\overrightarrow{F}=(4\hat{i}+\hat{j}-2\hat{k})N$
Velocity, $\overrightarrow{v}=(2\hat{i}+2\hat{j}+3\hat{k})m{s}^{-1}$
Power, $P=\overrightarrow{F}\cdot \overrightarrow{v}=(4\hat{i}+\hat{j}-2\hat{k})\cdot (2\hat{i}+2\hat{j}+3\hat{k})$
$=(8+2-6)W=4W$.