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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 26 February 2021, Shift 2, Physics Q8

Question 8 of 90 in this shift, Physics question 8 of 30, Section A.

A cord is wound round the circumference of wheel of radius r. The axis of the wheel is horizontal and the moment of inertia about it is I. A weight mg is attached to the cord at the end. The weight falls from rest. After falling through a distance ‘h’, the square of angular velocity of wheel will be :
  1. (1)2gh
  2. (2)2ghI+mr2\frac{2gh}{I + mr^2}
  3. (3)2mghI+mr2\frac{2mgh}{I + mr^2}Official answer
  4. (4)2mghI+2mr2\frac{2mgh}{I + 2mr^2}

Official answer

Option 3

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Work and Kinetic Energy
Idea tested
Conservation of Mechanical Energy

Same idea in other shifts

Asked 7× in all
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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.