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) Determine the pressure difference (in bar and in psi) between the inside and outside of an ultra-small air droplet near the surface of water given that the droplet diameter is

Answer :

Complete Question

The complete question is shown on the first uploaded image

Answer:

a

[tex]P = 292 \ bar[/tex]

[tex]P_{psi} = 4235.17 \ psi[/tex]

b

[tex]P = 2.92 \ bar[/tex]

[tex]P_{psi} = 42.3517 \ psi[/tex]

c

[tex]P = 2.92*10^{-5} \ bar[/tex]

[tex]P_{psi} = 0.0423517 \ psi[/tex]

Explanation:

From the question we are told that

    [tex]1 \ bar = 10^{5} Pa = 14.504 \ psi[/tex]

   [tex]\sigma_s = 0.073 \ N/m \ at \ 20^oC[/tex]

Generally the pressure difference is mathematically represented as

           [tex]P = \frac{2 \sigma_s }{r}[/tex]

Considering question a

Here  the diameter is  [tex]d = 10 nm = 10*10^{-9} \ m[/tex]

Generally the radius is mathematically represented as

         [tex]r = \frac{d}{2} = \frac{10*10^{-9}}{2} = 5*10^{-9} \ m[/tex]

So

         [tex]P = \frac{2 * 0.073 }{5*10^{-9}} \ Pa[/tex]

=>    [tex]P = 292 *10^{5}\ Pa[/tex]

Converting to bar

      [tex]P_{bar} = \frac{292 *10^{5}}{1*10^{5}}[/tex]

      [tex]P = 292 \ bar[/tex]

Converting to psi  

      [tex]P_{psi} = \frac{ 292 *10^{5}}{14.504}[/tex]

     [tex]P_{psi} = 4235.17 \ psi[/tex]

Considering question b

Here  the diameter is  [tex]d = 1\mu m = 1*10^{-6} \ m[/tex]

Generally the radius is mathematically represented as

         [tex]r = \frac{d}{2} = \frac{1*10^{-6}}{2} = 0.5*10^{-6} \ m[/tex]

So

         [tex]P = \frac{2 * 0.073 }{ 0.5*10^{-6}} \ Pa[/tex]

=>    [tex]P = 292 *10^{3}\ Pa[/tex]

Converting to bar

      [tex]P_{bar} = \frac{292 *10^{3}}{1*10^{5}}[/tex]

      [tex]P = 2.92 \ bar[/tex]

Converting to psi  

      [tex]P_{psi} = \frac{ 292 *10^{3}}{14.504}[/tex]

     [tex]P_{psi} = 42.3517 \ psi[/tex]

Considering question c

Here  the diameter is  [tex]d = 1mm = 1*10^{-3} \ m[/tex]

Generally the radius is mathematically represented as

         [tex]r = \frac{d}{2} = \frac{1*10^{-3}}{2} = 0.5*10^{-3} \ m[/tex]

So

         [tex]P = \frac{2 * 0.073 }{ 0.5*10^{-3}} \ Pa[/tex]

=>    [tex]P = 292 \ Pa[/tex]

Converting to bar

      [tex]P_{bar} = \frac{292 }{1*10^{5}}[/tex]

      [tex]P = 2.92*10^{-5} \ bar[/tex]

Converting to psi  

      [tex]P_{psi} = \frac{ 292 }{14.504}[/tex]

     [tex]P_{psi} = 0.0423517 \ psi[/tex]

     

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