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If vector vecP=a hati + a hatj +3hatk a...

If vector ` vecP=a hati + a hatj +3hatk and vecQ=a hati -2 hatj -hatk ` are perpendicular to each other , then the positive value of a is

A

3

B

1

C

2

D

0

Text Solution

Verified by Experts

The correct Answer is:
A
Vector ` vecP=a hati+ a hatj+ 3hatk` and vector ` vecQ=a hati -2hatj - hatk` .
If two vectors are perpendicular to each other , then ` vecP*vecQ=0 or ( a hati + a hatj+ 3 hatk)*( a hati-2 hatj -hatk)=0` or ` a^(2)-2a-3=0` .
Solving this quadratic equation, we get a=3 or -1 . Therefore positive value of a is 3 .
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