Question

Find the pressure inside a capillary tube of diameter 30 mm at a height of 0.5 mm from
the water level when it is immersed in water at 20 °G Surface tension of water at 20 °C
°C
is 0.0782N/m and the top surface of water is assumed to be parallel to the glass tube.
a) 3.75 Pa
b) 6.48 Pa
c) 5.11 Pa
d) 4.70 Pa​

Answer 1

Answer:

In the capillary tube, the water should rise to a height

H=

rρg

2T

Here T=73×10

−3

Nm, r=

2

0.50mm

=0.25×10

−3

m

ρ=10

3

kg/m

3

∴h=

0.25×10

−3

×10

3

×9.8

2×73×10

−3

=59×10

−3

m=59mm

Now h > r. i.e., length is outside water surface. Therefore, radius of meniscus> radius of capillary r.If R is the radius of meniscus. then we have

R

2T

=hρg

orR=

hρg

2T

Hereh=25mm=25×10

−3

m

R=

25×10

−3

×10

3

×9.8

2×73×10

−3

=0.6×10

−3

=0.6mm

Answer 2

Answer:

5.11pa

Step-by-step explanation:

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