Question

The position vector of 1 kg object is
$\stackrel{→}{r} = (3\hat{i} - \hat{j}) m$
and its velocity
$\stackrel{→}{v} = (3\hat{j} +\hat{k}) ms^{-1}.$
The magnitude of its angular momentum is √x Nm where x is

Answer 1

The correct answer is 91
$| \stackrel{→}{i} | = | \stackrel{→}{r} × (m\stackrel{→}{v}) |$
$= | ( 3\hat{i} - \hat{j} ) × ( 3\hat{j} + \hat{k} ) |$
$= | -\hat{i} - 3\hat{j} + 9\hat{k} |$
$= \sqrt{91}$
Therefore The magnitude of its angular momentum is $\sqrt{x}$ Nm where x is $\sqrt{91}$