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If $\vec{F} = (60\hat{i} + 15\hat{j} - 3\hat{k})$ N and $\vec{V} = (2\hat{i} - 4\hat{j} + 5\hat{k})$ m/s, then instantaneous power is :
A
195 watt
B
45 watt
C
75 watt
D
100 watt
Detailed Solution
Instantaneous power: $P = \vec{F}\cdot\vec{v}$
$P = (60\hat{i} + 15\hat{j} - 3\hat{k})\cdot(2\hat{i} - 4\hat{j} + 5\hat{k})$
$= (60)(2) + (15)(-4) + (-3)(5) = 120 - 60 - 15$
$P = 45$ watt
$P = (60\hat{i} + 15\hat{j} - 3\hat{k})\cdot(2\hat{i} - 4\hat{j} + 5\hat{k})$
$= (60)(2) + (15)(-4) + (-3)(5) = 120 - 60 - 15$
$P = 45$ watt