Question

The position of a particle is given by $\overrightarrow{r}=(\hat{i}+2\hat{j}-\hat{k})$ and momentum $\overrightarrow{p}=(\widehat{3i}+4\hat{j}-2\hat{k}).$ The angular momentum is perpendicular to

• A. X-axis
• B. Y-axis
• C. Z-axis
• D. Line at equal to all the three axes

Answer 1

The correct option is A X-axis

$\overrightarrow{L}=\overrightarrow{r}\times \overrightarrow{p}=\left|\begin{array}{ccc}\hat{i}& \hat{j}& \hat{k}\\ 1& 2& -1\\ 3& 4& -2\end{array}\right|=-\hat{j}-2\hat{k}$
i.e. the angular momentum is perpendicular to $x-$ axis.