Kg `ms^(-1)` is used to express

Options

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

Explanation

To determine what the unit kg m/s (kilogram meter per second) expresses, we can analyze the options provided: impulse, rate of change in momentum, pressure, or none of these.

### Step-by-Step Solution:

1. **Understanding the Units**:
- The unit kg m/s consists of:
- kg (kilogram) which is a unit of mass.
- m/s (meter per second) which is a unit of velocity.

2. **Analyzing Each Option**:
- **Impulse**:
- Impulse (J) is defined as the change in momentum.
- The formula for impulse is J = Δp, where Δp is the change in momentum.
- Momentum (p) is defined as mass times velocity (p = mv).
- Therefore, the unit of momentum is kg m/s.
- Thus, the unit of impulse is also kg m/s.

- **Rate of Change in Momentum**:
- The rate of change of momentum is defined as force (F).
- According to Newton's second law, F = dp/dt (where dp is the change in momentum and dt is the change in time).
- The unit of force is kg m/s², which is not the same as kg m/s.

- **Pressure**:
- Pressure (P) is defined as force per unit area (P = F/A).
- The unit of pressure is Newton per square meter (N/m²).
- Since 1 Newton (N) = kg m/s², the unit of pressure becomes kg/(m·s²), which is also not kg m/s.

3. **Conclusion**:
- Since kg m/s corresponds to the unit of impulse and does not match the units for rate of change in momentum or pressure, we conclude that kg m/s is used to express impulse.

### Final Answer:
Kg m/s is used to express **Impulse**.