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Question #42653

Difficulty: 8/10 | 🟢 Free

The Question

A solid non-conducting sphere of mass MM, radius RR, and total positive charge QQ is placed on a rough inclined plane that makes an angle heta=37∘ heta = 37^\circ with the horizontal. The incline slopes upwards to the right. The sphere has a non-uniform internal charge distribution such that its Effective Center of Charge (ECC) is located at a distance R/2R/2 vertically below its Center of Mass (CM). A uniform horizontal electric field of magnitude EE is applied in the rightward direction. The incline is sufficiently rough to prevent slipping. If the sphere remains in both translational and rotational equilibrium, what is the required magnitude of the electric field EE? (Take sin⁡37∘=3/5\sin 37^\circ = 3/5 and cos⁡37∘=4/5\cos 37^\circ = 4/5)

Options

  • A.

    2MgQ\frac{2Mg}{Q}

  • B.

    3Mg4Q\frac{3Mg}{4Q}

  • C.

    6Mg13Q\frac{6Mg}{13Q}

  • D.

    4Mg3Q\frac{4Mg}{3Q}

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Variable_Constraint

Develop pure symbolic logic skills by mastering algebraic constraints without relying on numerical data.

Concepts Behind This Question

Non-conducting Charged Sphere|Friction on Inclined Planes|Newton’s Third Law Pairing

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to distinguish between the Center of Mass (CM) and the Effective Center of Charge (ECC) in rigid body equilibrium.

A common trap is to treat the electrostatic force as acting at the CM, similar to gravity in a uniform field, which incorrectly yields zero electrostatic torque.

By placing the ECC vertically below the CM, the horizontal electric field generates a counter-clockwise torque that must be balanced by the clockwise torque from static friction.

Students who ignore the ECC displacement will incorrectly conclude that friction is zero (from torque equilibrium) and solve only the translational force balance, leading to the erroneous answer of 3Mg/4Q.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterElectric Charges and Fields - Class 12
ConceptNon-conducting Charged Sphere
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree