It is easier to pull boxes fitted with rollers because of ______

Options

A. Rolling friction
B. Sliding friction
C. lubricants
D. viscous force

Answer

To solve the question "It is easier to pull boxes fitted with rollers because of ______", we need to understand the concepts of friction involved in this scenario.

### Step-by-Step Solution:

1. **Understanding Friction**:
- Friction is the force that opposes the motion of an object. There are two main types of friction: sliding friction and rolling friction.

2. **Types of Friction**:
- **Sliding Friction**: This occurs when an object slides over a surface. It is generally higher and requires more force to overcome.
- **Rolling Friction**: This occurs when an object rolls over a surface, such as a wheel or roller. It is usually much lower than sliding friction.

3. **Role of Rollers**:
- When boxes are fitted with rollers, they can roll instead of sliding. This means that the friction encountered is rolling friction rather than sliding friction.

4. **Comparison of Friction Types**:
- Since rolling friction is less than sliding friction, it requires less force to move the box when it is on rollers.

5. **Conclusion**:
- Therefore, it is easier to pull boxes fitted with rollers because rolling friction is less than sliding friction.

The correct answer to fill in the blank is: "It is easier to pull boxes fitted with rollers because of rolling friction."