Complete the sentence. Friction always _______

Options

A. helps the motion
B. opposes the motion
C. both of these
D. none of these

Answer

**Step-by-Step Solution:**

1. **Understanding Friction**: Friction is a force that arises when two surfaces come into contact with each other. It is a contact force, meaning it only occurs when objects are in direct contact.

2. **Nature of Friction**: Friction can be influenced by the nature of the surfaces in contact. For example, rough surfaces create more friction compared to smooth surfaces. This is due to the microscopic irregularities on the surfaces that interlock.

3. **Direction of Friction**: The key characteristic of friction is that it always acts in the opposite direction to the motion of the object. If an object is sliding to the right, the frictional force will act to the left, opposing the motion.

4. **Conclusion**: Based on the understanding of friction and its properties, we can complete the sentence: "Friction always opposes the motion."

**Final Answer**: Friction always opposes the motion.

---