Q. The vector which can give unit vector along $x$-axis with $\overrightarrow{A} = 2\widehat{i} - 4\widehat{j} + 7\widehat{k}$,$\ \overrightarrow{B} = 7\widehat{i} + 2\widehat{j} - 5\widehat{k}$ and $\overrightarrow{C} = - 4\widehat{i} + 7\widehat{j} + 3\widehat{k}$ is
A) $4\widehat{i} + 5\widehat{j} + 5\widehat{k}$
B) $- 5\widehat{i} - 5\widehat{j} + 5\widehat{k}$
C) $- 4\widehat{i} - 5\widehat{j} - 5\widehat{k}$
D) $4\widehat{i} - 5\widehat{j} + 5\widehat{k}$
Explanation
(c) The vector is $\widehat{i} - \lbrack\overrightarrow{A} + \overrightarrow{B} + \overrightarrow{C}\rbrack$
$= \widehat{i} - \lbrack$(2$\widehat{i} - 4\widehat{j} + 7\widehat{k}$)+($\ 7\widehat{i} + 2\widehat{j} - 5\widehat{k}$)+($- 4\widehat{i} + 7\widehat{j} + 3\widehat{k}$)]
$= - 4\widehat{i} - 5\widehat{j} - 5\widehat{k}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.