Kinematics Question 149

Question: The angle between the two vectors $ \vec{A}=3\hat{i}+4\hat{j}+5\hat{k} $ and $ \vec{B}=3\hat{i}+4\hat{j}+5\hat{k} $ it’s [DPMT 2000]

Options:

A) 60°

B) Zero

C) 90°

D) None of these

Show Answer

Answer:

Correct Answer: D

Solution:

$ \cos \theta =\frac{\overrightarrow{A}.\overrightarrow{B}}{|A||B|}=\frac{9+16+25}{\sqrt{9+16+25}\sqrt{9+16+25}} $ = $ \frac{50}{50}=1 $
therefore $ \cos \theta =1 $
$ \therefore $ $ \theta ={{\cos }^{-1}}(1) $



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