Which of the following statements about friction is not correct?

Options

A. It tends to stop a moving object.
B. It allows us to walk and run without slipping.
C. Magnitude of rolling friction is greater than that of sliding friction.
D. Friction causes wastage of energy.

Explanation

To determine which statement about friction is not correct, let's analyze each option step by step:

1. **Statement 1: Friction tends to stop a moving object.**
- Friction always acts in the opposite direction of motion. This means that if an object is moving, friction will work to slow it down and eventually stop it. Therefore, this statement is **correct**.

2. **Statement 2: Friction allows us to walk and run without slipping.**
- Friction provides the necessary grip between our feet and the ground, preventing us from slipping when we walk or run. Without sufficient friction, we would easily slip. Hence, this statement is **correct**.

3. **Statement 3: The magnitude of rolling friction is greater than that of sliding friction.**
- This statement is incorrect. Rolling friction is generally much less than sliding friction. It is easier to roll an object than to slide it across a surface because the contact area is smaller in rolling. Thus, this statement is **not correct**.

4. **Statement 4: Friction causes wastage of energy.**
- Friction converts kinetic energy into thermal energy, which can be considered as energy wastage in many scenarios. This is a well-known fact about friction. Therefore, this statement is **correct**.

After analyzing all the statements, we conclude that the statement that is not correct is **Statement 3**: "The magnitude of rolling friction is greater than that of sliding friction."

### Final Answer:
The answer is **Option 3**.