Question

A liquid is at rest in a container. In a sphere of influence, the liquid molecule at its centre is

• A. attracted by other molecules in the sphere of influence.
• B. attracted by other molecules outside sphere of influence.
• C. repelled by other molecules outside the sphere of influence.
• D. repelled by other molecules in the sphere of influence.

Hint:

The molecule at the centre is pulled by neighbours within the sphere of influence.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Cohesive forces between liquid molecules are short ranged. The sphere of influence is the sphere of about \(10^{-9}\) m radius around a molecule, outside of which the force is negligible.

Step 2: Detailed Explanation:
A molecule at the centre of the sphere is attracted by the other molecules that lie inside the sphere. Since it is surrounded from all sides, the pulls are balanced and the net force on it is zero.
Molecules outside the sphere are too far away to exert a noticeable attraction, so options (B) and (C) are not the case. The force between liquid molecules at this range is attractive, so repulsion in (D) is not what acts.

Step 3: Final Answer:
Option (A): the molecule is attracted by the other molecules within the sphere of influence.

Final Answer:
A centre molecule is pulled by neighbours within its sphere. \[ \boxed{\text{(A) }\text{attracted by molecules inside the sphere}} \]