Question

If pi+qj is a unit vector perpendicular to 4i+3j, then

• A. P=$-3/5$ and q=-$4/5$
• B. P=$4/5$ and q=$3/5$
• C. P=$2/5$ and q=$1/5$
• D. None

Answer 1

Answer: (A)

P=$-3/5$ and q=-$4/5$

$pi+qj\perp 4i+3j$

$\Rightarrow (4i+3j)(pi+qj)=0$

$4p+3q=0$

$pq=\frac{-3}{4}$

$\therefore pi+qj=-3i+4j$

$p=\frac{-3}{5},q=\frac{4}{5}$