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Question: A force \((4\widehat{i} + \widehat{j} - 2\widehat{k})\) N acting on a body maintains its velocity at...

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

A

4 W

B

5 W

C

2 W

D

8 W

Answer

4 W

Explanation

Solution

Force, F→=(4i^+j^−2k^)N\overrightarrow{F} = (4\widehat{i} + \widehat{j} - 2\widehat{k})N

Velocity, v→=(2i^+2j^+3k^)mS−1\overrightarrow{v} = (2\widehat{i} + 2\widehat{j} + 3\widehat{k})mS^{- 1}

Power, P=F→.v→=(4i^+j¨−2k^).(2i^+2j^+3k^)P = \overrightarrow{F}.\overrightarrow{v} = (4\widehat{i} + \ddot{j} - 2\widehat{k}).(2\widehat{i} + 2\widehat{j} + 3\widehat{k})

=(8+2−6)W=4W= (8 + 2 - 6)W = 4W