Question

The position vector of an object at any time $t$ is given by $3t^2\hat{i}+6t\hat{j}+\hat{k}$. Its velocity along y-axis has the magnitude

• A. $6t$
• B. $6$
• C. $0$
• D. $9$

Answer 1

The correct option is B $6$

$\overrightarrow{r}=3t^2\hat{i}+6t\hat{j}+\hat{k}$
$\frac{d\overrightarrow{r}}{dt}=\overrightarrow{v}=6t\hat{i}+6\hat{j}$
$v_y=6m/s$