Properties of Matter 4 Question 17

19. When the gas bubble is at a height y from the bottom, its temperature is

(a) T0(p0+ρlgHp0+ρlgy)2/5

(b) T0(p0+ρlg(Hy)p0+ρlgH)2/5

(c) T0(p0+ρlgHp0+ρlgy)3/5

(d) T0(p0+ρlg(Hy)p0+ρlgH)3/5

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Answer:

Correct Answer: 19. 1720Ns/m2

Solution:

  1. When the tube is not there,

p+p0+12ρv12+ρgH=12ρv22+p0p+ρgH=12ρ(v22v12)A1v1=A2v2v1=A2v2A1p+ρgH=12×ρ[v22(A2A1v2)2]=12×ρ×v22[1(π(0.3)2π(0.9)2)2]=12×ρ×(10)2[1181]=4×103ρ81=4×103×90081=49×105N/m2

This is also the excess pressure Δp.

By Poiseuille’s equation, the rate of flow of liquid in the capillary tube

Q=π(Δp)a48ηl

8×106=(πa2)(Δp)8η(a2l)η=(πa2)(Δp)(a2l)8×8×106

Substituting the values, we have

η=(106)(49×105)(2×106)8×8×106=1720Ns/m2



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