Which one of the following is not a periodic motion?

Options

A. Rotation of the earth about its axis.
B. A freely suspended bar magnet displaced from its N-S direction and released.
C. Motion of hands of a clock.
D. An arrow released from a bow.

Explanation

To determine which of the following options is not a periodic motion, we need to first understand what periodic motion is. Periodic motion is defined as a motion that repeats itself after a fixed interval of time.

Let's analyze each option step by step:

1. **Rotation of the Earth about its axis**:
- The Earth rotates on its axis once every 24 hours. This means that the motion of the Earth is repeated after a fixed interval of time (24 hours).
- **Conclusion**: This is a periodic motion.

2. **Freely suspended bar magnet displaced from its north-south direction and released**:
- When a bar magnet is displaced from its equilibrium position (north-south direction) and released, it will oscillate back and forth around that position. This oscillation occurs at regular intervals.
- **Conclusion**: This is also a periodic motion.

3. **Motion of the hands of a clock**:
- The hands of a clock move in a circular motion and complete a full cycle at regular intervals: the second hand completes a cycle every 60 seconds, the minute hand every 60 minutes, and the hour hand every 12 hours.
- **Conclusion**: This is a periodic motion.

4. **An arrow released from the bow**:
- When an arrow is shot from a bow, it travels in a straight line away from the bow and does not return. There is no repetition of motion after a fixed interval of time.
- **Conclusion**: This is not a periodic motion.

Based on the analysis above, the option that is not a periodic motion is:

**Answer**: An arrow released from the bow.

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