WEBVTT
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This is College physics
Answers with Shaun Dychko.
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The pressure inside a balloon we're told
is one and a half centimeters of water.
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So that means the pressure will
raise water in a column up
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one and a half centimeters in
an open tube manometer.
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But anyway, we're going to convert that
into Pascals by using this formula here.
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So the pressure in a sphere due
to surface tension of a liquid
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is four times the surface tension
divided by the radius of the sphere.
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We can solve this for surface tension by
multiplying both sides by *r* over four.
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We get *gamma* is *P r* over four.
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The pressure is going to be the
pressure due to this column of water
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which is the density of water
times *g* times its height
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and so we substitute that
in for the pressure.
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So we have the effective
surface tension of the balloon
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which is sort of the
stretchiness of the rubber,
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is the one times ten to the three
kilograms per cubic meter density of water
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times 9.81 newtons per kilogram,
times one and a half centimeters
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which is times ten to the minus two meters,
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times ten times ten to the
minus two meters height,
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sorry radius of the balloon,
and divide that by four.
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You get 3.68 newtons per meter.
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Now this number is a lot more
than the surface tensions
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listed in the data table given to us
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and we expect that because
in the data table
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we're dealing with surface
tensions of liquids
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whereas this is an elastic soli\d and so
we expect the number to be bigger.