Which of the following quantites is a vector?

Options

A. Mass of proton
B. Energy of thermal neutron
C. Velocity
D. Volume

Answer

To determine which of the given quantities is a vector, we need to understand the characteristics of vector quantities. A vector quantity is defined by having both magnitude and direction. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Properties of Vector Quantities**:
- A vector quantity must have both magnitude (a numerical value) and direction (a specific orientation in space).

2. **Analyze the First Option: Mass of Protons**:
- Mass is a scalar quantity. It only has magnitude (e.g., 1.67 x 10^-27 kg for a proton) and no direction.
- **Conclusion**: Mass is not a vector.

3. **Analyze the Second Option: Energy of Thermal Neutron**:
- Energy is also a scalar quantity. It has magnitude (e.g., measured in joules) but does not have a direction.
- **Conclusion**: Energy is not a vector.

4. **Analyze the Third Option: Velocity**:
- Velocity is a vector quantity. It has both magnitude (e.g., 10 km/h) and direction (e.g., towards north).
- **Conclusion**: Velocity is a vector.

5. **Analyze the Fourth Option: Volume**:
- Volume is a scalar quantity. It has magnitude (e.g., 10 liters) but does not have a direction.
- **Conclusion**: Volume is not a vector.

6. **Final Conclusion**:
- Among the options provided, only velocity has both magnitude and direction. Therefore, the correct answer is **velocity**.