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Question #42634

Difficulty: 8/10 | 🟢 Free

The Question

A particle of mass m=1 kgm = 1 \text{ kg} is attached to a fixed support by a spring of force constant k=25 N/mk = 25 \text{ N/m}. The particle is subjected to a linear drag force Fd=−bvF_d = -bv, where b=4 kg/sb = 4 \text{ kg/s} and vv is the velocity of the particle. An external driving force F(t)=40cos⁡(5t)+40cos⁡(3t)F(t) = 40 \cos(5t) + 40 \cos(3t) (in Newtons, with tt in seconds) is applied to the particle along the direction of the spring. After a sufficiently long time, the system reaches a steady state. What is the average rate of energy dissipation by the drag force over a long time interval?

Options

  • A.

    272 \text{ W}

  • B.

    544 \text{ W}

  • C.

    512 \text{ W}

  • D.

    136 \text{ W}

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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

Superposition of SHMs|Conservative vs Non-conservative|Integration

Why This Question Is Tricky

Common Mistakes

This question tests the principle of linear superposition in driven-damped harmonic oscillators and the non-linear nature of energy dissipation.

Students often incorrectly assume that the total average power can be calculated by finding a single 'effective' amplitude or by directly adding the driving forces and ignoring the phase lag (a misapplication of the Work-Energy theorem).

The trap exploits the fact that while displacement and velocity superimpose linearly, power depends on the square of velocity.

Because the driving frequencies are distinct, the time-averaged cross-terms of velocity vanish, meaning the total average power is strictly the sum of the average powers of the individual frequency components.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterOscillations - Class 11 Part 2
ConceptSuperposition of SHMs
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree