Sponsor Area

Mechanical Properties Of Fluids

Question
CBSEENPH11018349

Water rises to a height 4.8cm in a certain capillary tube. When the same tube is dipped in some another liquid it falls by 12.5cm. Compare the surface tension of water and liquid. Density of liquid is 9.6 gm/cc and angle of contact of liquid is 120°.

Solution
Given, 

Rise in water = 4.8 cm 
Fall in water when tube is dipped in some other liquid = 12.5 cm
Density of liquid = 9.6 gm/cc
Angle of contact of liquid = 120o

The height to which the liquid rises or falls in the capillary tube is given by the relation,

                        h=2T cosθrpg 

The above relation can be simplified to 

                        T=rgph2 cos θ                    ....(1)

Let T1 and T2 be the surface tension of water and liquid respectively.

By using the equation (1), we have


T1T2=ρ1h1ρ2h2cosθ2cosθ1

Here, ρ1=1 gm/cc,        h1=4.8cm,        θ1=0°         ρ2=9.6gm/cc,      h2=-12.5cm,   θ2=120°    T1T2=1×4.89.6×(-1.25)cos 120°cos 0°=15