Select the correct alternative(s)

Options

A. elastic forces are always conservative
B. elastic forces are not always conservative
C. elastic forces are conservative only when Hooke's law is obeyed
D. elastic forces may be conservative even when Hooke's law is not obeyed

Answer

To solve the question regarding the nature of elastic forces and their conservativeness, we will analyze each of the provided options step by step.

### Step 1: Understanding Elastic Forces
Elastic forces are the forces that arise when a material is deformed (stretched or compressed) and attempt to restore the material to its original shape. These forces are related to the intermolecular arrangements within the material.

### Step 2: Evaluating Option 1
**Option 1: Elastic forces are always conservative.**
- A conservative force is defined as one where the work done in moving an object around a closed path is zero.
- In the case of materials like rubber, when they are stretched and then released, they do not return to their original state along the same path. Therefore, the work done is not zero.
- **Conclusion:** This statement is **incorrect**.

### Step 3: Evaluating Option 2
**Option 2: Elastic forces are not always conservative.**
- Since we established that in some cases (like rubber), the work done is not zero when returning to the original position, this indicates that elastic forces can be non-conservative.
- **Conclusion:** This statement is **correct**.

### Step 4: Evaluating Option 3
**Option 3: Elastic forces are conservative only when Hooke's law is obeyed.**
- Hooke's law states that the force exerted by a spring is proportional to the displacement from its equilibrium position, valid only within the elastic limit.
- However, there are cases where elastic forces can be conservative even when Hooke's law does not hold (e.g., certain materials that exhibit elastic behavior outside Hooke's law).
- **Conclusion:** This statement is **incorrect**.

### Step 5: Evaluating Option 4
**Option 4: Elastic forces may be conservative even when Hooke's law is not obeyed.**
- As discussed, there are instances where elastic forces can still be conservative despite not following Hooke's law (e.g., certain elastic materials).
- **Conclusion:** This statement is **correct**.

### Final Conclusion
Based on the evaluations:
- **Correct Options:** 2 and 4
- **Incorrect Options:** 1 and 3