Define Surface tension. Write its formula. What is its S.I unit?

Explanation

### Step-by-Step Solution:

1. **Definition of Surface Tension**:
Surface tension is defined as the property of a liquid's surface that causes it to behave like a stretched elastic membrane. This phenomenon occurs because the molecules at the surface of a liquid experience a net inward force due to cohesive forces with the molecules below them. As a result, the surface tends to contract and minimize its surface area.

2. **Formula for Surface Tension**:
The formula for surface tension (denoted by the symbol \( \gamma \)) is given by:
\[
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