MCQ
For a surface molecule:
- AThe net force on it is zero.
- BThere is a net downward force.
- CThe potential energy is more than that of a molecule inside.
- ✓Both $B$ and $D$
✓
Answer
Correct option: D.
Both $B$ and $D$
A molecule viewed from the top to surface of the fluid. Force exerted on a molecule by all nearby molecule are equal and opposite, so net horizontal component of force is zero. as a molecule is viewed horizontally to the surface of fluid a vertically downward force acts on molecule due to which it does not escape from surface.
There is a net attractive force on molecules at surface acting downwards.
So the $P.E$ of molecules at the surface is negative to lower ones but in magnitude $\text{PE(mgh)}$ is more than that of the lower or inside molecules.
There is a net attractive force on molecules at surface acting downwards.
So the $P.E$ of molecules at the surface is negative to lower ones but in magnitude $\text{PE(mgh)}$ is more than that of the lower or inside molecules.
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