Two glass plates are separated by water. If surface ension of water is 75 dyne/cm and area of each plate wetted by water is 8 cm2 and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is
102 dyne
104 dyne
105 dyne
106 dyne
C.
105 dyne
The shape of water layer between the two plates is shown in figure
Thickness d of the film = 0.12 mm
= 0.012 cm
Radius R of the cylindrical face =
Pressure difference across the surface
Area of each plate wetted by water = A
Force F required to separate the two plates is given by
F = pressure difference × area
=
Putting the given values, we get
F =
F = 105 dyne