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) _____.
Answer (integer)
101
Solution
Capillary rise
<br><br>h = ${{2T\cos \theta } \over {\rho gr}}$
<br><br>$\Rightarrow$ T = ${{\rho grh} \over {2\cos \theta }}$
<br><br>= $${{\left( {900} \right)\left( {10} \right)\left( {15 \times {{10}^{ - 5}}} \right)\left( {15 \times {{10}^{ - 2}}} \right)} \over 2}$$
<br><br>= 1012.5 $\times$ 10<sup>–4</sup>
<br><br>= 101.25 × 10<sup>–3</sup>
= 101.25 mN/m
<br><br>$\simeq$ 101.00 mN/m
About this question
Subject: Physics · Chapter: Properties of Solids and Liquids · Topic: Elasticity
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