Which of the folowing can be zero, when a particle is in motion for some time ?

Options

A. distance
B. displacement
C. speed
D. None of these

Answer

To determine which of the following quantities can be zero when a particle is in motion for some time, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Distance**:
- Distance is defined as the total path length traveled by a particle, regardless of the direction.
- Since the particle is in motion, it must have covered some distance. Therefore, distance cannot be zero when the particle is in motion.
- **Conclusion**: Distance cannot be zero.

2. **Understanding Displacement**:
- Displacement is defined as the shortest straight-line distance from the initial position to the final position of the particle, along with the direction.
- It is possible for a particle to return to its original position after moving. In this case, the initial and final positions are the same, resulting in a displacement of zero.
- **Example**: If a particle moves in a circular path and returns to its starting point, the displacement is zero.
- **Conclusion**: Displacement can be zero when the particle is in motion.

3. **Understanding Speed**:
- Speed is defined as the rate at which distance is covered. It is a scalar quantity and is always non-negative.
- For speed to be zero, the distance traveled must also be zero. Since the particle is in motion, it must have traveled some distance, meaning speed cannot be zero.
- **Conclusion**: Speed cannot be zero.

4. **Final Conclusion**:
- Among the options provided, the only quantity that can be zero while the particle is in motion is **displacement**.

### Answer:
The correct answer is **displacement (Option B)**.

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