Question

A body constrained to move along y-axis is subjected to a constant force $\vec{F} = -\hat{i}+2\hat{j}+3\hat{k}\,N$. The work done by this force in moving the body a distance of $4\, m$ along $y$-axis is

• A. $4\,J$
• B. $8\,J$
• C. $12\,J$
• D. $24\,J$

Answer 1

Answer: (B)

$8\,J$

Answer 2

Here, $\vec{F} = -\hat{i}+2\hat{j}+3\hat{k}\,N$ As the body moves a distance of $4\, m$ along $y$-axis, $\therefore \vec{d} = 4\hat{j}\,m$ Work done by the given force is $W = \vec{F} \cdot \vec{d} = \left(-\hat{i}+2\hat{j}+3\hat{k}\,N\right)\cdot\left(4\hat{j}\,m\right)= 8\,J$