Properties of Matter 4 Question 3

5. The pressure that has to be applied to the ends of a steel wire of length 10cm to keep its length constant when its temperature is raised by 100C is (For steel, Young’s modulus is 2×1011Nm2 and coefficient of thermal expansion is 1.1×105K1 )

(2014 Main)

(a) 2.2×108Pa

(b) 2.2×109Pa

(c) 2.2×107Pa

(d) 2.2×106Pa

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Answer:

Correct Answer: 5. (*)

Solution:

  1. The bubble will detach if,

sinθT×dl=T(2πr)sinθ

Buoyant force Surface tension force

43πR3ρwgT×dlsinθ(ρw)(43πR3)g(T)(2πr)sinθsinθ=rR

Solving, r=2ρwR4g3T=R22ρwg3T

No option matches with the correct answer.



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