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Question #42457

Difficulty: 8/10 | 🟢 Free

The Question

A solid cylinder of mass m=2 kgm = 2 \text{ kg} and radius RR is placed on a rough inclined plane inclined at an angle θ=60∘\theta = 60^\circ to the horizontal. The coefficient of static friction between the cylinder and the plane is μ=123\mu = \frac{1}{2\sqrt{3}}. A force FF is applied to the center of mass of the cylinder, directed upwards along the inclined plane. What is the minimum magnitude of FF required to ensure that the cylinder rolls down the incline without slipping? (Take g=10 m/s2g = 10 \text{ m/s}^2)

Options

  • A.

    53 N5\sqrt{3} \text{ N}

  • B.

    2533 N\frac{25\sqrt{3}}{3} \text{ N}

  • C.

    103 N10\sqrt{3} \text{ N}

  • D.

    15 N15 \text{ N}

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Multi-Concept_Bridge

Master problems that require linking physics and math concepts to solve complex competitive questions.

Concepts Behind This Question

Minimum Force to Move a Block|Rolling on Inclines

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to couple translational and rotational dynamics under the constraint of pure rolling.

A common trap is treating the cylinder as a point mass and simply balancing forces at the threshold of sliding (F=mgsin⁡θ−μmgcos⁡θF = mg \sin\theta - \mu mg \cos\theta), which yields the incorrect distractor 2533 N\frac{25\sqrt{3}}{3} \text{ N}.

This flawed approach ignores the torque required to maintain the angular acceleration α=a/R\alpha = a/R.

By requiring the static friction to simultaneously satisfy the rotational dynamic equation f=12maf = \frac{1}{2}ma and the static threshold f≤μNf \le \mu N, students must realize that the minimum force FF is dictated by the friction required to sustain pure rolling, not just translational equilibrium.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterLaws of Motion - Class 11 Part 1
ConceptMinimum Force to Move a Block
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree