alleryFind a unit vector in the direction of $\vec a = \hat i - 2\hat j$:
A$\hat i - 2\hat j$
B$(\hat i - 2\hat j)/\sqrt 5$
C$(\hat i - 2\hat j)/5$
D$(\hat i - 2\hat j)/3$
Answer & Solution
Correct answer: B. $(\hat i - 2\hat j)/\sqrt 5$
$|\vec a| = \sqrt{1^2 + 2^2} = \sqrt 5$.
Unit vector $\hat a = \vec a / |\vec a| = (\hat i - 2\hat j)/\sqrt 5$.
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