Question

A force of $2\widehat{i} + 3\widehat{j} + 4\widehat{k}\mspace{6mu} N$acts on a body for 4 second, produces a displacement of $(3\widehat{i} + 4\widehat{j} + 5\widehat{k})m.$ The power used is

• A. 9.5 W
• B. 7.5 W
• C. 6.5 W
• D. 4.5 W

Answer 1

Answer: (A)

9.5 W

Answer 2

$P = \frac { \vec { F } \cdot \vec { s } } { t } = \frac { ( 2 \hat { i } + 3 \hat { j } + 4 \hat { k } ) \cdot ( 3 \hat { i } + 4 \hat { j } + 5 \hat { k } ) } { 4 }$ $= \frac { 38 } { 4 } = 9.5 \mathrm {~W}$