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⚛️ Physics  ·  System of Particles and Rotational Motion  ·  NEET & JEE

A ring, a disk, and a solid sphere of equal mass and radius roll down an incline. Which reaches the bottom first?

Answer: Solid sphere.

  • A Solid sphere
  • B Disk
  • C Ring
  • D All at same time

Correct answer: A. Solid sphere

Explanation: The solid sphere has the smallest I/mR² ratio (2/5), so it has the greatest acceleration down the incline.

axis OPr⊥Fττ = r⊥ × F = r × F × sinθ

Torque about axis O equals the force F multiplied by the perpendicular distance r⊥ from the axis to the line of action of the force, producing rotation.

Concept context

Moment of inertia, torque, angular momentum, rolling motion. Very high JEE weightage.

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