For a particle executing simple harmonic motion, which of the following statements is not correct

Options

A. vertical oscillations of a spring
B. motion of simple pendulum
C. The motion of planets around the sun is periodic but not simple harmonic motion.
D. vertical oscillation of a wooden plank floating in a liquid

Explanation

To determine which statement is not correct regarding a particle executing simple harmonic motion (SHM), we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Simple Harmonic Motion (SHM)**:
- SHM is characterized by oscillatory motion that is periodic. This means that the motion repeats itself at regular intervals, and it occurs about a mean position.

2. **Analyzing Each Option**:
- **Option 1: Vertical oscillations of a spring**:
- A spring that is vertically oscillating will move up and down about a mean position. This is a classic example of SHM, as it satisfies both conditions of being oscillatory and periodic.
- **Conclusion**: This statement is correct.

- **Option 2: Motion of a simple pendulum**:
- A simple pendulum swings back and forth about a mean position. It also exhibits periodic motion and is oscillatory in nature.
- **Conclusion**: This statement is also correct.

- **Option 3: Motion of planets around the sun**:
- The motion of planets is periodic as they revolve around the sun, but it is not oscillatory. The planets do not move back and forth about a fixed position; they follow elliptical orbits.
- **Conclusion**: This statement is correct, but it is not a statement of SHM.

- **Option 4: Vertical oscillations of a wooden plank floating in liquid**:
- A wooden plank floating in liquid may oscillate, but this motion is not periodic. The energy loss due to damping (friction with the liquid) will eventually stop the oscillation, making it non-periodic.
- **Conclusion**: This statement is not correct as it does not represent SHM.

3. **Final Answer**:
- The statement that is not correct regarding simple harmonic motion is **Option 4: Vertical oscillations of a wooden plank floating in liquid**.