Assertion : Speed of any point on rigid body executing rolling motion can be calculated by expression `v =r omega`, where r is distance of point from instantaneous centre of rotation
Reason : Rolling motion of rigid body can be considered as a pure rotation about instantaneous centre of rotation.

Options

A. If both Assertion and Reason are correct and Reason is the correct explanation of Assertion
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
C. If Assertion is true but Reason is fasle
D. If Assertion is false but Reason is true

Explanation

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

### Step-by-Step Solution:

**Step 1: Understanding the Assertion**
- The assertion states that the speed of any point on a rigid body executing rolling motion can be calculated using the formula \( v = r \omega \), where \( r \) is the distance of the point from the instantaneous center of rotation.
- This formula is indeed valid for any point on a rigid body in rolling motion, where \( v \) is the linear speed, \( r \) is the distance from the instantaneous center of rotation, and \( \omega \) is the angular velocity.

**Step 2: Analyzing the Reason**
- The reason claims that rolling motion of a rigid body can be considered as a pure rotation about the instantaneous center of rotation.
- While rolling motion can be analyzed in terms of rotation, not all rolling motions can be considered pure rotation. For pure rotation, the condition \( v = r \omega \) must hold true for all points on the body, which is not always the case in rolling motion (for example, in cases of slipping).

**Step 3: Conclusion**
- The assertion is true because the formula \( v = r \omega \) can be used to calculate the speed of any point in rolling motion.
- The reason is false because not all rolling motions satisfy the condition for pure rotation.

### Final Answer:
- **Assertion**: True
- **Reason**: False