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

A solid sphere rolls without slipping down an incline of angle θ. The minimum coefficient of friction required is:

Answer: (2/7)tanθ.

  • A (2/7)tanθ
  • B (2/5)tanθ
  • C (1/7)tanθ
  • D (1/3)tanθ

Correct answer: A. (2/7)tanθ

Explanation: For a solid sphere the friction needed is f = (2/7)mg sinθ, and the normal force is mg cosθ, so μ<sub>min</sub> = (2/7)tanθ.

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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