Our hands heat up when we rub them together for a while. Explain why?

Explanation

**Step-by-Step Solution:**

1. **Understanding Friction:** When two surfaces come into contact and move against each other, friction is the force that opposes this motion. It acts in the opposite direction to the movement.

2. **Rubbing Hands Together:** When we rub our hands together, we are essentially sliding the surfaces of our hands against each other. This creates friction between the skin surfaces.

3. **Frictional Force:** As our hands move against each other, the frictional force acts to resist this motion. This resistance is what we feel as friction.

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