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Question #42434

Difficulty: 8/10 | 🟢 Free

The Question

A uniform rod of cross-sectional area AA, Young's modulus YY, and coefficient of linear expansion α\alpha is initially at a uniform temperature of 10∘C10^\circ\text{C}. It is placed horizontally on a smooth floor, wedged between two fixed rigid blocks. The faces of the blocks in contact with the rod are smooth inclined planes making an angle of 30∘30^\circ with the horizontal. The ends of the rod are cut to perfectly match the 30∘30^\circ incline. The rod is constrained by a smooth horizontal channel so that it cannot move vertically or bend. The ends of the rod are then maintained at steady temperatures of 90∘C90^\circ\text{C} and 50∘C50^\circ\text{C}, while its lateral surface is thermally insulated. Assuming the blocks do not deform, what is the magnitude of the normal force NN exerted by each inclined plane on the rod in the steady state?

Options

  • A.

    120AYα120 A Y \alpha

  • B.

    60AYα60 A Y \alpha

  • C.

    30AYα30 A Y \alpha

  • D.

    403AYα40\sqrt{3} A Y \alpha

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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

Normal Force at Angles|Steady State Temperature Gradient|Young's Modulus Sensitivity

Why This Question Is Tricky

Common Mistakes

This question tests the coupling of thermo-elasticity with static equilibrium under geometric constraints.

A common trap is treating the rod as a simple 1D free body and assuming the normal force equals the internal thermal stress (N=FN = F).

Another trap is incorrectly resolving the normal force vector (e.g., N=Fsin⁡θN = F \sin\theta instead of Nsin⁡θ=FN \sin\theta = F).

Furthermore, students must correctly apply the steady-state temperature gradient to find the average thermal strain, avoiding the mistake of using the boundary temperatures directly.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterLaws of Motion - Class 11 Part 1
ConceptNormal Force at Angles
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree