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Question #42614

Difficulty: 8/10 | 🟢 Free

The Question

A block of mass m=1 kgm = 1 \text{ kg} is attached to a fixed wall by a light spring of force constant k=100 N/mk = 100 \text{ N/m}. The block rests on a horizontal surface. The natural length of the spring is at x=0x = 0. The surface is perfectly smooth for x≥0.16 mx \ge 0.16 \text{ m} and rough for x<0.16 mx < 0.16 \text{ m} with a coefficient of kinetic friction μk=0.2\mu_k = 0.2. A stationary block of mass M=3 kgM = 3 \text{ kg} is placed exactly at the boundary x=0.16 mx = 0.16 \text{ m}. Block mm is pulled to x=0.20 mx = 0.20 \text{ m} and released from rest. When it reaches x=0.16 mx = 0.16 \text{ m}, it undergoes a perfectly inelastic collision with block MM, and they stick together. Find the maximum compression of the spring during the subsequent motion. (Take g=10 m/s2g = 10 \text{ m/s}^2)

Options

  • A.

    2.0 cm2.0 \text{ cm}

  • B.

    4.3 cm4.3 \text{ cm}

  • C.

    6.4 cm6.4 \text{ cm}

  • D.

    17.1 cm17.1 \text{ cm}

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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

Energy Partitioning|Impulse-Momentum Theorem|Static Friction Threshold|Approximations

Why This Question Is Tricky

Common Mistakes

This problem tests the student's ability to correctly partition energy in a system interrupted by an inelastic 'stick' event (collision).

The primary trap is the erroneous application of the work-energy theorem over the entire interval from release to maximum compression.

Students often assume that the initial spring potential energy is simply dissipated by friction and converted into the final spring potential energy, completely missing the instantaneous, non-conservative kinetic energy loss during the perfectly inelastic collision at the boundary.

By forcing the student to use the impulse-momentum theorem to find the new state vector (velocity) post-collision, the problem transitions from a conservative SHM phase to a discontinuous energy decay phase.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterOscillations - Class 11 Part 2
ConceptEnergy Partitioning
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree