Question

4. The lower end of the capillary tube of diameter 2mm is dipped 8cm below the surface of water in a beake
What is the pressure required in the tube in order to blow a hemispherical bubble at its end in water in
surface tension of water is 7.3 x 10 Nm. Given, 1 atm pressure = 1.01 x 10' Pa, density of water = 1000 kgm
g=9.8 ms. Also calculate excess pressure.
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Answer 1

Answer:Pressure required in the tube= 1.0193*10^5 Pa. Excess Pressure= 146 Pa.Now Check out the attachment.

Answer 2

(I). The pressure required in the tube is $1.02\times10^{5}\ Pa$

(II). The excess pressureis 146 Pa.

Explanation:

Given that,

Diameter = 2 mm

Height = 8 cm

Surface tension $T=7.3\times10^{-2}\ Nm$

Density of water = 1000 kg/m³

We need to calculate the pressure required in the tube

Using formula of pressure

$P=P_{0}+\rho g h+\dfrac{2T}{r}$

Where, g = acceleration due to gravity

h = height

T = surface tension

Put the value into the formula

$P=1.01\times10^5+1000\times9.8\times0.08+\dfrac{2\times7.3\times10^{-2}}{1\times10^{-3}}$

$P=1.02\times10^{5}\ Pa$

We need to calculate the excess pressure

Using formul of excess pressure

$P'=\dfrac{2S}{r}$

Put the value into the formula

$P'=\dfrac{2\times7.3\times10^{-2}}{1\times10^{-3}}$

$P'=146\ Pa$

Hence, (I). The pressure required in the tube is $1.02\times10^{5}\ Pa$

(II). The excess pressureis 146 Pa.

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Topic : Pressure

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