JEE Main 2015PhysicsMathematics in PhysicsHardMCQ

JEE Main 2015 — Mathematics in Physics Question with Solution

JEE Main 2015 (11 Apr Online)

Question

A vector A→ is rotated by a small angle ∆θ radians ∆θ≪1 to get a new vector B→ . In that case B→-A→ is :

Choose an option

Show full solutionCorrect option: C
Correct answer
CA→∆θ

Step-by-step explanation

B→=A→

B→-A→=A→2+A→2+2A→A→cos180°-∆θ

=A→2+A→2-2A→2cos∆θ

=2A→2-2A→2cos∆θ

=2A→21-cos∆θ

∵1-cos∆θ=2sin2∆θ2

=2A→2×2sin2∆θ2

=2A→sin∆θ2

For small ∆θ, sin∆θ2≃∆θ2

B→-A→=2A→∆θ2

=A→ ∆θ

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About this question

This is a previous-year question from JEE Main 2015, covering the Mathematics in Physics chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.