1.

Air is introduced through a nozzle into a tank  of  water to form a stream of bubbles. If the bubbles are intended to  have a diameter of  2 mm, calculate by how much the pressure of the air at the nozzle must exceed that of  the surrounding water. Assume that  σ  = 72.7 × 10−3  N m−1.

Answer»

Surface tension (\(\sigma\)) = 72.7 x 10-3 N/m 

Radius of bubble (r) = 1 

Formula: 

\(\Delta\)p = 2\(\sigma\)/r 

Calculations: 

\(\Delta\)p = 2 x 72.7 x 10-3 / 1 = 145.4 N/m2 

That is, the pressure of the air at the tip of nozzle must exceed the pressure of surrounding water by 145.4 N/m2



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