Which of the following in not the unit of surface tension ?

Options

A. `"newton"//"metre"`
B. `"joule"//("metre")^(2)`
C. `"kg"//("second")^(2)`
D. `"watt"//"metre"`

Explanation

To determine which of the following is not a unit of surface tension, we need to understand what surface tension is and how it is measured.

### Step-by-Step Solution:

1. **Definition of Surface Tension**:
Surface tension is defined as the force acting along the surface of a liquid per unit length. It can be expressed mathematically as:
\[ \text{Surface Tension} (\gamma) = \frac{\text{Force} (F)}{\text{Length} (L)} \]

2. **Units of Surface Tension**:
- The SI unit of force is Newton (N), and the unit of length is meter (m).
- Therefore, the unit of surface tension can be expressed as:
\[ \text{Unit of Surface Tension} = \frac{\text{N}}{\text{m}} = \text{N/m} \]

3. **Alternative Units**:
- We can also express Newton in terms of its base units:
\[ 1 \text{ N} = 1 \text{ kg} \cdot \frac{\text{m}}{\text{s}^2} \]
- Substituting this into the surface tension unit gives:
\[ \text{N/m} = \frac{\text{kg} \cdot \text{m/s}^2}{\text{m}} = \text{kg/s}^2 \]

4. **Joule per Meter Square**:
- Surface tension can also be related to energy per unit area. Since work (energy) is measured in Joules (J), and area is measured in square meters (m²), we can express surface tension as:
\[ \text{Surface Tension} = \frac{\text{J}}{\text{m}^2} \]
- Since \(1 \text{ J} = 1 \text{ N} \cdot \text{m}\), we can derive:
\[ \frac{\text{J}}{\text{m}^2} = \frac{\text{N} \cdot \text{m}}{\text{m}^2} = \frac{\text{N}}{\text{m}} = \text{N/m} \]

5. **Identifying Incorrect Unit**:
- Now, we need to identify which of the given options is not a unit of surface tension. The options typically include:
- N/m (correct)
- J/m² (correct)
- kg/s² (correct)
- V/m (incorrect)
- The unit V/m (volts per meter) is a unit of electric field strength and is not related to surface tension.

### Conclusion:
The unit that is not a unit of surface tension is **V/m**.