Question

S.I unit for the surface tension is:
A. $\dfrac{kg}{{{m}^{3}}}$
B. $\dfrac{kg}{{{m}^{2}}}$
D. $\dfrac{kg}{m}$
E. $\dfrac{N}{m}$

Answer 1

Hint: Surface tension is given by the formula. Surface tension is defined as force acting per unit length. An S.I unit can also be determined by the formula.

Complete answer:
Definition of Surface Tension: We can define surface tension as the intermolecular forces in between the particles of water, draw the liquid particles together. Along the surface, the particles are pulled toward the rest of the liquid.
Surface tension is defined as,
“The ratio of the surface force F to the length L along which the force acts”
As we know, the Force S.I unit is Newton.
And S.I unit of Length is Metre.
So by using the above concept and definitions in our given question, we can choose the correct option.
S.I unit of surface tension is $\dfrac{Newton}{Metre}$

So now we can say that, option D is correct.

Additional information:
Surface tension: The attractive forces between liquid molecules are responsible for surface tension. As we know, molecules at the surface do not have other like molecules on all sides of them and consequently they attract more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed. The surface tension of a liquid results from an imbalance of intermolecular attractive forces, the attractive forces between molecules:
1. A molecule in the bulk liquid experiences attractive forces with other molecules in all directions.
2. A molecule at the surface of a liquid experiences only net inward attractive forces
Why are other options incorrect?
Option A, Option B, Option C, are incorrect because
1. Force is never measured in kilograms.
2. In option A and option B, cubic metre and metre square is used. But cubic metre comes for volume measurement and metre square for area.

Note: When answering questions like these that are based on S.I units always clear your basic concepts about forces and where this force is acting on. For example, this force is acting per unit length. In one kind of force that is stress, force acts on per unit area.
S.I units should be calculated with the help of formula.