JEE Main 2021PhysicsRotational MotionMediumMCQ

JEE Main 2021 — Rotational Motion Question with Solution

JEE Main 2021 (27 Aug Shift 1)

Question

A huge circular arc of length 4.4 ly subtends an angle 4s at the centre of the circle. How long it would take for a body to complete 4 revolution if its speed is 8 AU per second?
Given : 1 ly=9.46×1015 m

1 AU=1.5×1011 m

Choose an option

Show full solutionCorrect option: B
Correct answer
B4.5×1010 s

Step-by-step explanation

ℓ=4.4ly=4.4×9.46×1015

length of Arc. =ℓ=Rθ

4.4×9.46×1015=Rθ

θ=4 S=4×4.843×10-6=1.94×10-5 rad

4.4×9.46×1015=R×1.94×10-5

R=2.1455×1021 meter

Speed =8Au=8×1.5×1011 ms-1=12×1011 ms-1

4 revolution means distance =4×2πR metre

time = distance  speed =4×2πR12×1011; time =8×3.14×2.1455×102112×1011⇒4.5×1010sec

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About this question

This is a previous-year question from JEE Main 2021, covering the Rotational Motion 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.