Which of the following is a correct statement ?

Options

A. Distance is the magnitude of displacement in all cases.
B. When a body moves with uniform speed, then the average speed is same as instantaneous speed.
C. Average speed is greater than the average velocity if a body is moving in a straight line without reversing its direction
D. When a body moves with constant velocity, the average velocity is zero.

Answer

To determine which of the statements is correct, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Option 1: Distance is the magnitude of displacement in all cases.**
- **Analysis:** This statement is incorrect. Distance is the total path length traveled by an object, while displacement is the shortest distance from the initial to the final position, including direction. In cases where the path is not a straight line, the distance can be greater than the magnitude of displacement. Therefore, this statement is false.

2. **Option 2: When a body moves with uniform speed, then the average speed is the same as the instantaneous speed.**
- **Analysis:** This statement is correct. When an object moves with uniform speed, its speed does not change over time. Thus, the average speed (total distance traveled divided by total time) equals the instantaneous speed (speed at any given moment). Therefore, this statement is true.

3. **Option 3: Average speed is greater than the average velocity if a body is moving in a straight line without reversing its direction.**
- **Analysis:** This statement is incorrect. If a body moves in a straight line without changing direction, the distance traveled is equal to the displacement. Therefore, the average speed (total distance/time) will be equal to the average velocity (total displacement/time). Hence, this statement is false.

4. **Option 4: When a body moves with constant velocity, the average velocity is zero.**
- **Analysis:** This statement is also incorrect. If a body moves with constant velocity, it means it is moving in a straight line at a constant speed. The average velocity will be equal to the constant velocity and will not be zero unless the body does not move at all. Therefore, this statement is false.

### Conclusion:
The correct statement among the options provided is **Option 2**: "When a body moves with uniform speed, then the average speed is the same as the instantaneous speed."

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