`Kgms^(-1)` used to express

Options

A. impulse
B. rate of change in momentum
C. pressure
D. None of these

Answer

To determine what `kg m s^(-1)` (kilogram meter per second) is used to express, we can analyze the options provided in the question step by step.

### Step 1: Understanding the Units
The unit `kg m s^(-1)` can be broken down as follows:
- `kg` represents mass (kilograms).
- `m` represents distance (meters).
- `s^(-1)` represents time (seconds) in the denominator.

### Step 2: Analyzing the Options
1. **Impulse**: Impulse is defined as the change in momentum, which can also be expressed as the product of force and time. The unit of impulse is `Newton second`, which can be converted to `kg m s^(-1)`. Therefore, impulse can be expressed in `kg m s^(-1)`.

2. **Rate of Change in Momentum**: The rate of change of momentum is defined as force. The unit of force is `Newton`, which is `kg m s^(-2)`. This does not match `kg m s^(-1)`.

3. **Pressure**: Pressure is defined as force per unit area. The unit of pressure is `Pascal`, which is equivalent to `N/m^2` or `kg m s^(-2) m^(-2)`, simplifying to `kg m s^(-2) m^(-2)`. This also does not match `kg m s^(-1)`.

4. **None of These**: This option would imply that none of the previous options are correct.

### Step 3: Conclusion
From the analysis, we can conclude that `kg m s^(-1)` is used to express **Impulse**.

Thus, the answer is:
- **Impulse (Option 1)**.