Q. 18
Consider a small surface area of 1 mm2 at the top of a mercury drop of radius 4.0 mm. Find the force exerted on this area to) by the air above it (b) by the mercury below it and (c) by the mercury surface in contact with it. Atmospheric pressure = 1.0 × 105 Pa and surface tension of mercury = 0.465 N m-1. Neglect the effect of gravity. Assume all numbers to be exact.
Answer :
(a) 0.1 N
(b) 0.10023 N
(c) 0.00023 N
Given, area of the small region,
Atmospheric pressure,
Surface tension of mercury,
(a) Force exerted by air above it is
(b) Pressure from inside the drop,
Total pressure=
Total force,
(c)Here, only the pressure from mercury bubble is to be considered.
Total force,
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