Kinematics Question 580
Question: If the resultant of the vectors $ 3\widehat{i}+4\widehat{j}+5\widehat{k} $ and $ 5\widehat{i}+3\widehat{j}+4\widehat{k} $ makes an angle $ \theta $ with x-axis, then $ cos90{}^\circ $ it’s
Options:
A) 0.07
B)0.574
C) 0.111
D)0.123
Show Answer
Answer:
Correct Answer: B
Solution:
[b] The resultant vector$ =( 3\hat{i}+4\hat{j}+5\hat{k} )+( 5\hat{i}+3\hat{j}+4\hat{k} )=8\hat{i}+7\hat{j}+9\hat{k} $
$ \cos \theta =\frac{8}{\sqrt{8^{2}+7^{2}+9^{2}}}=0.574 $
