N `m^(2)//kg^(2)` is a unit of

Options

A. surface tension
B. permittivity
C. gravitational constant
D. torque

Explanation

To determine what the unit \( N \cdot m^{2}/kg^{2} \) represents, we can analyze the options provided and break down the units involved.

### Step-by-Step Solution:

1. **Understanding the Units:**
- The unit \( N \) (Newton) is defined as \( kg \cdot m/s^{2} \).
- Therefore, \( N \cdot m^{2} \) can be expressed as:
\[ N \cdot m^{2} = (kg \cdot m/s^{2}) \cdot m^{2} = kg \cdot m^{3}/s^{2} \]

2. **Combining the Units:**
- Now, we need to divide this by \( kg^{2} \):
\[ \frac{kg \cdot m^{3}/s^{2}}{kg^{2}} = \frac{m^{3}}{kg \cdot s^{2}} \]

3. **Identifying the Physical Quantity:**
- The unit \( \frac{m^{3}}{kg \cdot s^{2}} \) corresponds to the gravitational constant \( G \) in the formula for gravitational force:
\[ F = G \frac{m_{1} m_{2}}{r^{2}} \]
- Here, \( G \) is expressed in units of \( N \cdot m^{2}/kg^{2} \), which matches our derived unit.

4. **Conclusion:**
- Therefore, the unit \( N \cdot m^{2}/kg^{2} \) is the unit of the gravitational constant \( G \).

### Final Answer:
The unit \( N \cdot m^{2}/kg^{2} \) is a unit of the gravitational constant \( G \).

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