KVPY SX SB Exam 2018 Question Paper

Question : 22 of 120

Marks: +1, -0

Air (density

p

) is being blown on a soap film (surface tension

T

) by a pipe of radius

R

with its opening right next to the film. The film is deformed and a bubble detaches from the film when the shape of the deformed surface is a hemisphere. Given that the dynamic pressure on the flim due to the air blown at speed v is

1/2ρ v^2

,the speed at which the bubble is formed is

$√{ T /{ρR}}$
$√{{ 2T }/{ρR}}$
$√{{ 4T}/ {ρR}}$
$√{{8T}/ {ρR}}$

Validate

Solution:

1/2ρ v^ 2 ={4T}/R

v=√{{8T}/ {ρR}}

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