What is the origin of forces between two surfaces in contact ?

Explanation

### Step-by-Step Solution

1. **Understanding Contact Forces**: When two surfaces are in contact, they exert forces on each other. These forces are categorized as contact forces, which arise due to the interaction of the surfaces.

2. **Identifying Friction Force**: The primary force that originates between two surfaces in contact is known as the friction force. This force is crucial in determining how the surfaces interact when an attempt is made to move one surface over the other.

3. **Direction of Friction**: The friction force always acts in the opposite direction to the motion (or attempted motion) of the surfaces in contact. For example, if one surface is trying to slide over another, the friction force will act to oppose that sliding motion.

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