Assertion: Every periodic motion is not simple harmonic motion.
Reason: The motion governed by the force law F=-kx is simple harmonic.

Options

A. If both assertion and reson are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

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

### Step 1: Understand the Assertion
The assertion states: "Every periodic motion is not simple harmonic motion."
- **Periodic Motion**: This is defined as motion that repeats itself after a fixed interval of time. Examples include the motion of a pendulum, the rotation of a wheel, or the oscillation of a spring.
- **Simple Harmonic Motion (SHM)**: This is a specific type of periodic motion where the restoring force is directly proportional to the displacement from the mean position and acts in the opposite direction. The mathematical representation of this restoring force is given by \( F = -kx \), where \( k \) is a constant and \( x \) is the displacement.

### Step 2: Analyze the Assertion
The assertion is true because not all periodic motions are simple harmonic. For example, the motion of a clock's hands is periodic but not simple harmonic.

### Step 3: Understand the Reason
The reason states: "The motion governed by the force law \( F = -kx \) is simple harmonic."
- This statement is also true because it describes the condition under which an object exhibits simple harmonic motion.

### Step 4: Determine the Relationship Between Assertion and Reason
Now we need to see if the reason correctly explains the assertion. The assertion is about the nature of periodic motion, while the reason describes a specific case of simple harmonic motion.

### Conclusion
Both the assertion and the reason are true, but the reason does not serve as a correct explanation for the assertion. The assertion is a broader statement about periodic motion, while the reason is a specific case of simple harmonic motion.

### Final Answer
Based on the analysis, the correct option is:
- **Option 2**: Both assertion and reason are true, but reason is not the correct explanation of assertion.