Vector Algebra Question 389
Question: The unit normal vector to the line joining $ \mathbf{i}-\mathbf{j} $ and $ 2,\mathbf{i}+3,\mathbf{j} $ and pointing towards the origin is
[MP PET 1989]
Options:
A) $ \frac{4,\mathbf{i}-\mathbf{j}}{\sqrt{17}} $
B) $ \frac{-4,\mathbf{i}+\mathbf{j}}{\sqrt{17}} $
C) $ \frac{2,\mathbf{i}-3,\mathbf{j}}{\sqrt{13}} $
D) $ \frac{-,2,\mathbf{i}+3,\mathbf{j}}{\sqrt{13}} $
Show Answer
Answer:
Correct Answer: B
Solution:
- $ \vec{L}=\mathbf{i}+4\mathbf{j} $ Therefore, vector perpendicular to $ \vec{L}=\lambda (4\mathbf{i}-\mathbf{j}) $ \ Unit vector is $ \frac{4\mathbf{i}-\mathbf{j}}{\sqrt{17}}. $ But it points towards origin
$ \therefore $ Required vector $ =\frac{-4\mathbf{i}+\mathbf{j}}{\sqrt{17}}. $
BETA
