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Question #43009

Difficulty: 8/10 | 🟢 Free

The Question

A solid conducting sphere of radius RR and total charge Q>0Q > 0 is rigidly fixed at the origin of a reference frame attached to a spacecraft. The spacecraft is accelerating in deep space with a constant acceleration a⃗=qQ16πϵ0mR2i^\vec{a} = \frac{qQ}{16\pi\epsilon_0 m R^2} \hat{i}, where ϵ0\epsilon_0 is the vacuum permittivity. A small particle of mass mm and charge q>0q > 0 is projected from the position x=3Rx = 3R on the x-axis towards the origin, with an initial speed v0v_0 relative to the spacecraft. Assume the charge QQ remains uniformly distributed on the sphere. What is the minimum value of v0v_0 required for the particle to strike the surface of the sphere?

Options

  • A.

    qQ12πϵ0mR\sqrt{ \frac{qQ}{12\pi\epsilon_0 m R} }

  • B.

    qQ3πϵ0mR\sqrt{ \frac{qQ}{3\pi\epsilon_0 m R} }

  • C.

    7qQ12πϵ0mR\sqrt{ \frac{7qQ}{12\pi\epsilon_0 m R} }

  • D.

    5qQ24πϵ0mR\sqrt{ \frac{5qQ}{24\pi\epsilon_0 m R} }

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Intuition_Breaker

Train your brain to resist "obvious" answers that are designed to deceive your intuition.

Concepts Behind This Question

Trajectory of Charged Particle|Charged Conducting Sphere|Potential Gradient Direction

Why This Question Is Tricky

Common Mistakes

This question tests the application of the Work-Energy Theorem in a non-inertial reference frame, specifically focusing on the superposition of a conservative electric field and a uniform pseudo-field.

The primary trap is treating the electric potential as the sole energy barrier.

Students often fail to account for the work done by the pseudo-force (or make a sign error by assuming it opposes the motion), which effectively tilts the potential landscape.

By projecting the particle against the electric gradient but along the pseudo-force direction, the problem forces students to correctly integrate both contributions to find the true effective potential barrier.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterMoving Charges and Magnetism - Class 12
ConceptTrajectory of Charged Particle
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree