Question

A vector P = 3i-2j+ak is perpendicular to the vector Q=2i +j-k, The value of a is:
a. 2 b.1 c.4 d.3

Answer 1

Answer:

P. Q=0 bcz P perpendicular to Q

P.Q= 3*2-2*1-a*1

0=6-2-a

0=4-a

a=4

Answer 2

The value of a is 4. (Option c)

Given:

Vector P and vector Q are perpendicular

vector P = 3i - 2j + ak

vector Q = 2i + j -k

To find:

Value of a

Solution:

If two vectors are perpendicular, then their scalar product (dot product) is zero.

Since vectors, P and Q are perpendicular to each other

    P.Q = 0

⇒ (3i - 2j + ak).(2i + j - k) = 0

⇒ 6 - 2 - a = 0

⇒ 4 - a = 0

⇒ a = 4

Therefore, the value of a is 4