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JEE Advanced 2023Paper 2
Exam
JEE Advanced
Year
2023
Paper
Paper 2
Subject
Physics
Chapter
Mechanical Properties of Fluids

JEE Advanced 2023 · Paper 2 · Physics · Mechanical Properties of Fluids

A cylindrical furnace has height (H) and diameter (D) both 1m . It...

A cylindrical furnace has height (H)\left(H\right) and diameter (D)\left(D\right) both 1m1m. It is maintained at temperature 360K360K. The air gets heated inside the furnace at constant pressure Pa{P}_{a} and its temperature becomes T=360KT = 360K. The hot air with density ρρ rises up a vertical chimney of diameter d=0.1md = 0 . 1m and height h=9mh = 9m above the furnace and exits the chimney (see the figure). As a result, atmospheric air of density ρa=1.2kgm−3{ρ}_{a} = 1 . 2kg{m}^{- 3}, pressure Pa{P}_{a} and temperature Ta=300K{T}_{a} = 300K enters the furnace. Assume air as an ideal gas, neglect the variations in ρandTρ and T inside the chimney and the furnace. Also ignore the viscous effects.

[Given: The acceleration due to gravity g=10ms−2andπ=3.14g = 10m{s}^{- 2} and \pi = 3 . 14]

A cylindrical furnace has height (H) and diameter (D) both 1m . It is maintained at temperature 360K . The air gets


When the chimney is closed using a cap at the top, a pressure difference ∆P∆ P develops between the top and the bottom surfaces of the cap. If the changes in the temperature and density of the hot air, due to the stoppage of air flow, are negligible then the value of ∆P∆ P is _____ Nm−2N{m}^{- 2}.

Correct answer

0

Step-by-step solution

Applying Bernoulli’s theorem between top and bottom points of furnace :

Pa+12ρaV2=Pa+ρgH+12ρV2...(1){P}_{a} + \dfrac{1}{2}{ρ}_{a}{V}^{2} = {P}_{a} + ρgH + \dfrac{1}{2}ρ{V}^{2} . . . \left(1\right)

Also, since PM=ρRTPM = ρRT

⇒ρa×300=ρ×360⇒ {ρ}_{a} \times 300 = ρ \times 360

⇒ρ=1kgm−3...(2)⇒ ρ = 1kg{m}^{- 3} . . . \left(2\right)

From equation(1), we can write

⇒V22(0.2)=1×10×1⇒ \dfrac{{V}^{2}}{2}\left(0 . 2\right) = 1 \times 10 \times 1

⇒V=10ms−1⇒ V = 10m{s}^{- 1}

Now, let V′V ' be the speed of air in chimney.

⇒⇒ By continuity equation,

πD24⋅V=πd24⋅V′\dfrac{\pi{D}^{2}}{4} \cdot V = \dfrac{\pi{d}^{2}}{4} \cdot V '

⇒V′=100V=1000ms−1⇒ V ' = 100V = 1000m{s}^{- 1}

Therefore, pressure difference ∆p∆ p

=ρV′2⋅= ρV{'}^{2} \cdotarea

=1×(1000)2×πd24=1×(1000)2×3.14×(0.1)24=7850Nm2= 1 \times {\left(1000\right)}^{2} \times \dfrac{\pi{d}^{2}}{4} = 1 \times {\left(1000\right)}^{2} \times \dfrac{3 . 14 \times {\left(0 . 1\right)}^{2}}{4} = 7850N{m}^{2}

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