Which one of the following statements concerning momentum is true?

Options

A. Momentum is a force.
B. Momentum is a scalar quantity.
C. The SI unit of momentum is kg `m^2//s`.
D. Momentum and impulse are measured in the same units.

Answer

To determine which statement concerning momentum is true, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze Statement A**: "Momentum is a force."
- Momentum (p) is defined as the product of mass (m) and velocity (v), i.e., \( p = mv \).
- Force (F) is defined as the rate of change of momentum, given by \( F = \frac{dp}{dt} \).
- Therefore, momentum is not a force; it is a quantity that describes motion.
- **Conclusion**: Statement A is **false**.

2. **Analyze Statement B**: "Momentum is a scalar quantity."
- Momentum is a vector quantity because it has both magnitude and direction.
- It is calculated as the product of mass (a scalar) and velocity (a vector), which results in a vector.
- **Conclusion**: Statement B is **false**.

3. **Analyze Statement C**: "SI unit of momentum is square per second."
- The SI unit of mass is kilograms (kg) and the SI unit of velocity is meters per second (m/s).
- Therefore, the SI unit of momentum is \( kg \cdot m/s \), not square per second (m²/s²).
- **Conclusion**: Statement C is **false**.

4. **Analyze Statement D**: "Momentum and impulse are measured in the same unit."
- Impulse (I) is defined as the product of force (F) and the time duration (t) for which the force acts, i.e., \( I = F \cdot t \).
- Since force is the rate of change of momentum, the units of impulse (N·s) are equivalent to the units of momentum (kg·m/s).
- Thus, momentum and impulse indeed have the same units.
- **Conclusion**: Statement D is **true**.

### Final Answer:
The correct statement concerning momentum is **D**: "Momentum and impulse are measured in the same unit."

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