A force of left( {2widehat i + 3widehat j + 4widehat k} right),N acts on a body for 4, sec and

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5.Work, Energy, Power and Collision

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A force of $\left( {2\widehat i + 3\widehat j + 4\widehat k} \right)\,N$ acts on a body for $4\, sec$ and produces a displacement of $\left( {3\widehat i + 4\widehat j + 5\widehat k} \right)\,m$. The power used is :- ............... $\mathrm{W}$

A

$4.5$

B

$6.5$

C

$7.5$

D

$9.5$

Solution

$P=\frac{\overrightarrow{F} \cdot \overrightarrow{S}}{t}=\frac{(2 \hat{i}+3 \hat{j}+4 \hat{k}) \cdot(3 \hat{i}+4 \hat{j}+5 \hat{k})}{4}$

$=\frac{6+12+20}{4}=9.5$ Watt

Standard 11

Physics

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