Answer:
The assertion is true and reason is false.
Explanation:
Assertion: I P+ Q I = I P- QI, then P must be perpendicular to Q.
Reason : The relation will hold even when Q is a null vector.
Now
[tex]\left | P + Q \right |=\left | P - Q \right |\\\\P^2 + Q^2 + 2 P Q cos \theta =P^2 + Q^2 - 2 P Q cos \theta\\\\4 P Q cos \theta = 0 \\\\cos \theta = 0 \\\\\theta = 90 degree[/tex]
So, P and Q are perpendicular to each other.
So, the assertion is true.
Reason is false.
