Assertion: When an object is accelerating, it is either speeding up or slowing down.
Reason: When an object moves on a circular path with uniform speed, the object accelerates.

Options

A. both assertion and reason are correct and reason is a correct explanation of the assertion.
B. both assertion and reason are correct but reason is not the correct explanation of assertion.
C. assertion is correct but reason is incorrect
D. assertion is incorrect but reason is correct.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states: "When an object is accelerating, it is either speeding up or slowing down."

- **Analysis**: Acceleration is defined as the rate of change of velocity. Velocity has both magnitude and direction. Therefore, an object can accelerate not only by changing its speed (magnitude) but also by changing its direction while maintaining the same speed.

### Step 2: Understand the Reason
The reason states: "When an object moves on a circular path with uniform speed, the object accelerates."

- **Analysis**: In uniform circular motion, the speed of the object remains constant, but its direction changes continuously. Since velocity is a vector quantity (having both magnitude and direction), a change in direction means that the velocity is changing, which implies that there is acceleration present.

### Step 3: Conclusion
Now we can conclude the validity of both statements:

- The assertion is **false** because an object can accelerate without speeding up or slowing down if it is changing direction (as in uniform circular motion).
- The reason is **true** because an object in uniform circular motion does indeed accelerate due to the continuous change in direction.

### Final Answer
Since the assertion is false and the reason is true, the correct option is **D**.

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