Assertion : Strain is a unitless quantity.
Reason : Strain is equivalent to force

Options

A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. Assertion is true but Reason is false.
D. Both Assertion and Reason are false.

Explanation

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
- **Assertion**: Strain is a unitless quantity.
- **Explanation**: Strain is defined as the ratio of the change in length (ΔL) to the original length (L). Mathematically, it is expressed as:
\[ \text{Strain} = \frac{\Delta L}{L} \]
Since both ΔL and L are measured in the same units (length), when we take the ratio, the units cancel out. Therefore, strain is indeed a unitless quantity.

### Step 2: Analyze the Reason
- **Reason**: Strain is equivalent to force.
- **Explanation**: This statement is incorrect. Strain is not equivalent to force; rather, it is a measure of deformation per unit length. Force, on the other hand, is a physical quantity that is measured in newtons (N) and is related to mass and acceleration (according to Newton's second law). Thus, strain and force are fundamentally different concepts.

### Conclusion
- The assertion is true: Strain is a unitless quantity.
- The reason is false: Strain is not equivalent to force.

### Final Answer
The correct option is: **C** - Assertion is true, but the reason is false.

---