Start Learning Free

Before You Begin

Question #42352

Difficulty: 8/10 | 🟢 Free

The Question

A heavy parent nucleus is modeled as a rigid thin rod of length LL with a non-uniform linear mass density λ(x)=λ0(1+2xL)\lambda(x) = \lambda_0\left(1 + \frac{2x}{L}\right) for 0≤x≤L0 \le x \le L. It is initially rotating with a constant angular velocity ω\omega about an axis perpendicular to the rod passing through its geometric center, which is at rest in the laboratory frame. The nucleus undergoes fission by splitting exactly at its geometric center into two fragments. The binding energy per unit mass of the parent nucleus is B1B_1 and that of both fragments is B2B_2 (B2>B1B_2 > B_1). Assume all available energy in the center-of-mass (COM) frame is converted entirely into the relative translational kinetic energy of the fragments. What is the relative speed vrelv_{rel} of the two fragments immediately after fission?

Options

  • A.

    12815(B2−B1)+44135L2ω2\sqrt{ \frac{128}{15} (B_2 - B_1) + \frac{44}{135} L^2 \omega^2 }

  • B.

    12815(B2−B1)+1645L2ω2\sqrt{ \frac{128}{15} (B_2 - B_1) + \frac{16}{45} L^2 \omega^2 }

  • C.

    8(B2−B1)+1136L2ω2\sqrt{ 8 (B_2 - B_1) + \frac{11}{36} L^2 \omega^2 }

  • D.

    12815(B2−B1)\sqrt{ \frac{128}{15} (B_2 - B_1) }

Check Your Answer

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

Center of Mass (COM) Frame|Binding Energy per Nucleon Curve|Integration

Why This Question Is Tricky

Common Mistakes

This question tests the ability to distinguish between the laboratory frame and the center-of-mass (COM) frame in a variable-mass/fission scenario.

A common trap is assuming the initial kinetic energy available for the fragments is simply the rotational energy about the geometric center (IGCI_{GC}).

However, because the mass distribution is non-uniform, the COM is shifted from the geometric center, meaning the COM is translating in the lab frame.

Students must correctly apply the parallel axis theorem to find ICOMI_{COM} and use the reduced mass of the asymmetric fragments to find the true relative velocity.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterSystem of Particles and Rotational Motion - Class 11 Part 1
ConceptCenter of Mass (COM) Frame
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree