Question

A particle moves with ,a velocity $(5\hat{i}-3\hat{j}+6\hat{k})$ m/s under the influence of a constant force $\vec{F}=10\hat{i}+10\hat{j}+12\hat{k}N.$ The instantaneous power applied to the particle is:

• A. 200 J/s
• B. 40 J/s
• C. 140 J/s
• D. 170 J/s

Answer 1

Answer: (C)

140 J/s

Answer 2

$\overrightarrow{V}=(5\hat{i}-3\hat{j}+6\hat{k})m/s$ $\overrightarrow{F}=(10\hat{i}+10\hat{j}+20\hat{k})N$ $\therefore$ Power $\overrightarrow{P}=\overrightarrow{F}.\overrightarrow{v}$ $=(10\hat{i}+10\hat{j}+20\hat{k}).(5\hat{i}-3\hat{j}+6\hat{k})$ $=50-30+120$ $=140\,W$