Question

In a surface tension experiment, with a capillary tube, water rises to a height of 5 cm in the capillary tube. If the same experiment is repeated in an artificial satellite revolving around the earth then the water will rise in the capillary tube up to a height equal to:
A. 3cm
B. 6cm
C. 9.8cm
D. Full length of the capillary tube

Answer 1

Hint: In this question we have to apply the concept of the surface tension acting on a liquid when an experiment is conducted with it. We have to find what happens if the same experiment is conducted in outer space in an artificial satellite which is revolving around the earth.

Complete step by step answer:
In a surface tension experiment the water rises to a height of 5 centimetre when the experiment is done on earth.
But we have to consider the case when the same experiment is being conducted on an artificial satellite in outer space. In such a condition there is no effective Gravity in outer space. The force exerted by the surface tension will not be balanced by the weight of the liquid. And the force of surface tension will be an unbalanced force.
The force exerted due to the surface tension is given by the following expression:
$S.T\,Force = 2\pi rT\cos \theta $
In this expression, $\theta $ is the angle the surface makes with the wall of the tube.
Since the surface tension force will be unbalanced in outer space the surface tension will exert as much force as possible, corresponding to which the water level will rise to the very top. After reaching the top, the angle between the wall and the liquid becomes ${90^ \circ }$ and when the angle becomes ${90^ \circ }$ then the value of the force becomes zero because $\cos {90^ \circ }$ is zero and liquid stops at that point. Therefore, the liquid rises up to the full length of the tube in which the experiment is being conducted.

The correct option is option (D).

Note:
These types of questions can be answered with basic understanding of the situation. Since any gravity is not present in outer space the surface tension will be an unbalanced force. Students should be able to make this kind of assertion and then the question can be easily solved by them.