Name the force which always oppose motion.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the force that always opposes motion. This requires knowledge of forces acting on objects in motion.

2. **Identifying the Force**: The force that opposes motion is known as friction. It is a force that arises when two surfaces are in contact with each other.

3. **Explanation of Friction**: Friction acts in the opposite direction to the motion of an object. For example, if an object is sliding to the right, the friction force will act to the left, opposing the motion.

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