Question

physics a level ques help explain in detail plz thx

Answer 1

Imagine a beaker containing the liquid and a vertical straw (not an inclined straw).


Atmospheric pressure p0 acts on the surface of the liquid.


Now, the child is sucking at top of the straw with a pressure of 0.9p0 (since the child is capable of lowering the pressure at the top of the straw by 10%). As the child sucks up the liquid rises up the straw of length h.


The difference in pressure at the surface of the liquid in the beaker (= p0) and the pressure at the top of the straw (= 0.9p0) is represented by the pressure due to the column of liquid in the straw (= hρg).


p0 – 0.9p0 = hρg

hρg = 0.1p0 = p0 / 10

Length of straw, h = p0 / 10ρg