How many objects in the following undergo combined motion?
Motion of earth, wheels on a bicycle, rolling ball, table fan, sewing machine

Explanation

To determine how many objects undergo combined motion from the given list, we need to analyze the type of motion each object exhibits.

### Step-by-Step Solution:

1. **Motion of Earth**:
- The Earth undergoes two types of motion:
- **Rotation**: The Earth spins on its axis.
- **Revolution**: The Earth orbits around the Sun.
- Therefore, the motion of the Earth is a combined motion (rotation + revolution).

2. **Wheels on a Bicycle**:
- The wheels of a bicycle perform:
- **Rotational Motion**: The wheels rotate around their axes.
- **Translational Motion**: The bicycle moves forward as the wheels rotate.
- Hence, the wheels on a bicycle also exhibit combined motion (rotational + translational).

3. **Rolling Ball**:
- A rolling ball exhibits:
- **Rotational Motion**: The ball spins around its axis.
- **Translational Motion**: The ball moves forward as it rolls.
- Thus, a rolling ball also shows combined motion (rotational + translational).

4. **Table Fan**:
- A table fan primarily has:
- **Circular Motion**: The blades of the fan rotate in a circular path.
- However, since the entire fan does not move from one place to another, it does not exhibit combined motion. It only has circular motion.

5. **Sewing Machine**:
- A sewing machine performs:
- **Rotational Motion**: The needle moves up and down in a circular path.
- **Oscillatory Motion**: The needle also moves back and forth.
- Therefore, the sewing machine exhibits combined motion (rotational + oscillatory).

### Conclusion:
Now, we can summarize the findings:
- Objects that undergo combined motion:
- Motion of Earth (1)
- Wheels on a bicycle (2)
- Rolling ball (3)
- Sewing machine (4)
- Object that does not undergo combined motion:
- Table fan (1)

Thus, the total number of objects that undergo combined motion is **4**.

### Final Answer:
**4 objects undergo combined motion.**

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