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Model Paper 8 — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysicsModel Paper 81 Mark
MCQ
Assertion (A): If $\vec{A}$ is parallel to $\vec{B}$ then $\vec{A} \times \vec{B}$ is a null vector.
Reason (R): The magnitude cross product of two vectors is given by, $|\vec{A} \times \vec{B}|= AB \sin \theta$.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
✓

Answer

(a) Both A and R are true and R is the correct explanation of A .
Explanation: As, $\vec{A} \| \vec{B}, \therefore \theta=0 \Rightarrow \vec{A} \times \vec{B}= AB \sin 0=\overrightarrow{0}$
ie. $\vec{A} \times \vec{B}$ is a null vector. Where null vector is a vector whose magnitude is zero but has a direction.

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