Motion in a Plane - Result Question 8
10. If the angle between the vectors $\vec{A}$ and $\vec{B}$ is $\theta$, the value of the product $(\vec{B} \times \vec{A}) \cdot \vec{A}$ is equal to
(a) $B A^{2} \sin \theta$
(b) $B A^{2} \cos \theta$
(c) $B A^{2} \sin \theta \cos \theta$
(d) zero
[2005]
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Answer:
Correct Answer: 10. (d)
Solution:
(d) $(\vec{B} \times \vec{A}) \cdot \vec{A}=\vec{C} \cdot \vec{A}=C A \cos 90^{\circ}=0$.
Dot product of any two perpendicular vector is zero.
