Friction can be __________ (increased/reduced) by using ball bearings between the moving parts of machines.

Explanation

**Step-by-Step Solution:**

1. **Understanding Friction Types**:
- Friction is the resistance that one surface or object encounters when moving over another. There are different types of friction, primarily static friction, sliding (kinetic) friction, and rolling friction.

2. **Identifying the Context**:
- The question specifically refers to the use of ball bearings in machines. Ball bearings are small, spherical objects that are used to reduce friction between moving parts.

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