Explain the difference between solid friction and viscosity.

Explanation

To explain the difference between solid friction and viscosity, we can break down the concepts into several key points:

### Step-by-Step Solution:

1. **Definition of Solid Friction**:
- Solid friction, also known as dry friction, occurs when two solid surfaces slide against each other. It is the resistance to motion that one surface or object encounters when moving over another.

2. **Definition of Viscosity**:
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