Topic: Engineering Mathematics
$\vec{p}=2i-3j$, $\vec{Q}=-3i+4j-2k$ and $\vec{R}$ are in equilibrium, if $\vec{R}$ is
- A. $-i-j+2k$
- B. $i-j+2k$
- C. $i+j+2k$
- D. $i-j-2k$
Answer: B. $i-j+2k$
Explanation: For the vectors to be in equilibrium, their sum must be zero: $\vec{p}+\vec{Q}+\vec{R}=0$. Therefore, $\vec{R}=-(\vec{p}+\vec{Q})=-((2-3)i+(-3+4)j+(0-2)k)=-(-i+j-2k)=i-j+2k$.