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The projection of the vector a⃗=i^+2j^−3k^\vec{a} = \hat{i} + 2\hat{j} - 3\hat{k} on the vector 2i^+6j^+3k^2\hat{i} + 6\hat{j} + 3\hat{k} is

Solution

✅ Correct Option: 2

The projection of vector a⃗\vec{a} on vector b⃗\vec{b} is given by:

Projection=a⃗⋅b⃗∣b⃗∣\text{Projection} = \dfrac{\vec{a} \cdot \vec{b}}{|\vec{b}|}


Here, a⃗=i^+2j^−3k^\vec{a} = \hat{i} + 2\hat{j} - 3\hat{k} and b⃗=2i^+6j^+3k^\vec{b} = 2\hat{i} + 6\hat{j} + 3\hat{k}

The dot product is found by multiplying matching components and adding them up:

a⃗⋅b⃗=(1)(2)+(2)(6)+(−3)(3)\vec{a} \cdot \vec{b} = (1)(2) + (2)(6) + (-3)(3)

=2+12−9= 2 + 12 - 9

=5= 5


The magnitude of b⃗\vec{b}:

∣b⃗∣=(2)2+(6)2+(3)2|\vec{b}| = \sqrt{(2)^2 + (6)^2 + (3)^2}

=4+36+9= \sqrt{4 + 36 + 9}

=49= \sqrt{49}

=7= 7


Substituting into the formula:

Projection=a⃗⋅b⃗∣b⃗∣\text{Projection} = \dfrac{\vec{a} \cdot \vec{b}}{|\vec{b}|}

=57= \dfrac{5}{7}


The projection of a⃗\vec{a} on b⃗\vec{b} is

57\boxed{\dfrac{5}{7}}

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