Question 297: Properties of Matter

Question

When a long glass capillary tube of radius
0.015 cm is dipped in a liquid, the liquid rises
to a height of 15 cm within it. If the contact angle
between the liquid and glass to close to 0o, the
surface tension of the liquid, in milliNewton m–1,
is [$$\rho $$(liquid) = 900 kgm–3, g = 10 ms–2] (Give answer
in closest integer) _____.

Accepted Answer

Capillary rise
h = $${{2T\cos 	heta } \over {ho gr}}$$
$$ \Rightarrow $$ T = $${{ho grh} \over {2\cos 	heta }}$$
= $${{\left( {900} ight)\left( {10} ight)\left( {15 	imes {{10}^{ - 5}}} ight)\left( {15 	imes {{10}^{ - 2}}} ight)} \over 2}$$
= 1012.5 $$ 	imes $$ 10
Ã¢ÂÂ4
= 101.25 ÃÂ 10
Ã¢ÂÂ3
= 101.25 mN/m
$$ \simeq $$ 101.00 mN/m

Properties of Matter

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