Question

If the projection of \[ \vec a = 5\hat i+\hat j+\lambda\hat k \] on \[ \vec b = 2\hat i+6\hat j+3\hat k \] is \(4\) units, then \(\lambda=\)

• A. \(6\)
• B. \(4\)
• C. \(5\)
• D. \(3\)

Hint:

Scalar projection formula: \[ \text{proj}_{\vec b}\vec a = \frac{\vec a\cdot\vec b}{|\vec b|} \] Always compute the dot product first and then divide by the magnitude.

Answer 1

The Correct Option is B