Which of the following is a one-dimensional motion ?

Options

A. Landing of an aircraft
B. Earth revolving around the sun
C. Motion of wheels of moving
D. Train running on a straight track

Answer

To determine which of the given options represents one-dimensional motion, we will analyze each option step by step.

### Step 1: Understand the concept of one-dimensional motion
One-dimensional motion refers to motion that occurs along a straight line. In such motion, an object can only move forward or backward along that line, without any deviation in other dimensions.

### Step 2: Analyze each option

1. **Landing of an aircraft**:
- When an aircraft lands, it moves along a runway, which is a straight line. However, the aircraft also has vertical motion (descending towards the ground) and lateral motion (approaching from the side). Therefore, this is not purely one-dimensional motion.

2. **Earth moving around the Sun**:
- The Earth's orbit around the Sun is elliptical, which involves motion in two dimensions (the plane of the orbit). Thus, this is also not one-dimensional motion.

3. **Motion of a wheel of a moving vehicle**:
- A wheel rotates while also translating along a path. The motion of the wheel involves both rotational motion and translational motion, which means it is not confined to one dimension.

4. **Train running on a straight track**:
- A train moving along a straight track is an example of one-dimensional motion. The train can only move forward or backward along the track without any lateral deviation.

### Step 3: Conclusion
Based on the analysis, the correct answer is:
**Option 4: Train running on a straight track is a one-dimensional motion.**

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