Choose the correct statement(s) for a cricket ball that is spinning clockwise through air
S1 : Streamlines of air are symmetric around the ball
S2 : The velocity of air above the ball relative to it is larger than that below the ball.
S3 : The velocity of air above the ball relative to it is smaller than that below the ball.
S4 : There is a net upward force on the ball.

Options

A. S1, S2 and S4
B. S2 and S4
C. S4 only
D. S3 only

Explanation

To solve the question regarding the behavior of a spinning cricket ball in air, we will analyze each statement one by one based on the principles of fluid mechanics, particularly the Bernoulli's principle and the Magnus effect.

### Step-by-Step Solution:

1. **Understanding the Spin and Motion of the Ball**:
- The cricket ball is spinning clockwise while moving forward through the air. This rotation affects the airflow around the ball.

2. **Analyzing Statement S1**:
- **Statement S1**: "Streamlines of air are symmetric around the ball."
- **Analysis**: As the ball spins, the streamlines of air above the ball become closer together (indicating higher velocity), while those below the ball are further apart (indicating lower velocity). Therefore, the streamlines are not symmetric.
- **Conclusion**: **S1 is incorrect**.

3. **Analyzing Statement S2**:
- **Statement S2**: "The velocity of air above the ball relative to it is larger than that below the ball."
- **Analysis**: Due to the clockwise spin, the air above the ball moves faster than the air below it. This is because the upward motion of the ball adds to the forward motion of the air above, while it subtracts from the forward motion of the air below.
- **Conclusion**: **S2 is correct**.

4. **Analyzing Statement S3**:
- **Statement S3**: "The velocity of air above the ball relative to it is smaller than that below the ball."
- **Analysis**: This statement contradicts the analysis of S2. The air above the ball is moving faster than the air below it, not slower.
- **Conclusion**: **S3 is incorrect**.

5. **Analyzing Statement S4**:
- **Statement S4**: "There is a net upward force on the ball."
- **Analysis**: Due to the difference in air velocity, there is a pressure difference created by the Bernoulli effect. The pressure below the ball is higher than the pressure above it, resulting in a net upward force on the ball, known as the Magnus effect.
- **Conclusion**: **S4 is correct**.

### Final Answer:
- The correct statements are **S2 and S4**.