Question

What is the magnitude of \[\vec{a}=\vec{i}-2\vec{j}\]?

Options

• \[3\]

• \[\sqrt{5}\]

• \[\sqrt{3}\]

• \[5\]

Answer 1

The components of \[\vec{a}\] are \[1\] and \[-2\]. Its magnitude is \[|\vec{a}|=\sqrt{1^2+(-2)^2}=\sqrt{5}\].