Question

Work done when a force $\overrightarrow{F}=(\hat{i}+2\hat{j}+3\hat{k})N$ acting on a particle takes it from the point $\overrightarrow{r_1}=(\hat{i}+\hat{j}+\hat{k})$ to the point $\overrightarrow{r_2}=(\hat{i}-\hat{j}+2\hat{k})$ is

• A. -3 J
• B. -1 J
• C. zero
• D. 2 J

Answer 1

The correct option is B -1 J

Work done is equal to $\overline{F}.\Delta \overline{r}$
$\Delta \overline{r}={\overline{r}}_2-{\overline{r}}_1=-2\hat{j}+\hat{k}$
$W=\overline{F}\times \overline{r}=(\hat{i}+2\hat{j}+3\hat{k}).(-2\hat{j}+\hat{k})$
$\therefore W=-2+1=-1J$