Which of the following physical quantities is not conserved?

Options

A. Energy
B. Linear momentum
C. Force
D. Mass

Answer

To determine which physical quantity is not conserved among the given options, we will analyze each option based on the principles of conservation in physics.

### Step-by-Step Solution:

1. **Identify the Given Quantities**: The options provided are:
- Energy
- Linear Momentum
- Force
- Mass

2. **Understand Conservation Laws**:
- **Conservation of Energy**: Energy can neither be created nor destroyed; it can only change forms (e.g., from potential to kinetic energy).
- **Conservation of Linear Momentum**: In a closed system, the total linear momentum remains constant if no external forces act on it.
- **Conservation of Mass**: Mass is conserved in a closed system, meaning it cannot be created or destroyed.

3. **Analyze Each Quantity**:
- **Energy**: As per the conservation laws, energy is conserved.
- **Linear Momentum**: Linear momentum is also conserved in the absence of external forces.
- **Mass**: Mass is conserved in closed systems according to the law of conservation of mass.
- **Force**: Unlike the other quantities, force is not a conserved quantity. It is an interaction that can change depending on the circumstances and does not have a conservation law associated with it.

4. **Conclusion**: Since energy, linear momentum, and mass are all conserved quantities, the only quantity that is not conserved is **Force**.

5. **Final Answer**: Therefore, the physical quantity that is not conserved is **Force**.