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Question #42442

Difficulty: 8/10 | 🟢 Free

The Question

A block of mass m=2 kgm = 2 \text{ kg} and density ρ=8000 kg/m3\rho = 8000 \text{ kg/m}^3 is released from rest on a rough inclined plane of angle θ=37∘\theta = 37^\circ. The entire setup is submerged in a large tank containing a viscous fluid of density σ=2000 kg/m3\sigma = 2000 \text{ kg/m}^3. The coefficient of kinetic friction between the block and the plane is μ=0.25\mu = 0.25. The fluid exerts a drag force Fd=kv2F_d = k v^2 on the block, where k=0.6 kg/mk = 0.6 \text{ kg/m} and vv is the instantaneous velocity. Assuming the fluid is deep enough, what is the terminal velocity of the block? (Take g=10 m/s2g = 10 \text{ m/s}^2, sin⁡37∘=3/5\sin 37^\circ = 3/5)

Options

  • A.

    10 m/s\sqrt{10} \text{ m/s}

  • B.

    403 m/s\sqrt{\frac{40}{3}} \text{ m/s}

  • C.

    253 m/s\sqrt{\frac{25}{3}} \text{ m/s}

  • D.

    15 m/s\sqrt{15} \text{ m/s}

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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

Friction on Inclined Planes|Archimedes' Buoyancy Dynamics|Integration

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to correctly construct a free-body diagram in a buoyant medium.

A common trap is treating the normal force as mgcos⁡θmg \cos\theta and the driving force as mgsin⁡θmg \sin\theta, ignoring that buoyancy acts vertically upwards and reduces the effective weight of the body.

Consequently, both the normal force (which dictates kinetic friction) and the effective gravitational pull along the incline are modulated by the factor (1−σ/ρ)(1 - \sigma/\rho).

Failing to apply buoyancy to either the normal force or the driving force leads to the incorrect terminal velocities presented in the options.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterLaws of Motion - Class 11 Part 1
ConceptFriction on Inclined Planes
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree