What is the purpose of using ball bearings in machines ?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Function of Ball Bearings:**
- Ball bearings are mechanical components that allow for smooth movement between parts of a machine. Their primary purpose is to facilitate rotation or linear motion.

2. **Reduction of Friction:**
- One of the main purposes of using ball bearings is to reduce friction between moving parts. Friction is the resistance that one surface or object encounters when moving over another.

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