Question
Calculate the force required to take away a flat circular plate of radius 5cm and mass 2gm from the surface of water. The surface tension of water is 72 dyne/cm.
Solution
Given,
Radius of the circular plate, r = 5 cm
Mass, m = 2 gm
Surface tension of water, T = 72 dyne/cm
Weight of plate is, W = mg=2 x 980 = 1960 dyne
The circumference of circular plate is given by,
The down pull on plate due to surface tension is given by,
Therefore, total force required to take plate away from water surface is,
F=W+f
=1960+2260.8
=4220.8 dyne
