Sliding Friction vs. Static Friction

Definition:
Sliding friction is the force that resists the motion of two surfaces sliding against each other. Static friction, on the other hand, is the force that keeps an object at rest and prevents it from moving when a force is applied.

Explanation:
- Sliding friction is smaller than static friction because when an object is at rest, the microscopic roughness of the surfaces is more interlocked, leading to a higher resistance to motion. This is known as static friction.
- When the object starts moving, the surfaces are no longer fully interlocked, and the resistance to motion decreases, resulting in sliding friction being smaller than static friction.

Factors Affecting Sliding Friction:
- The nature of the surfaces in contact: Smoother surfaces will have lower sliding friction compared to rough surfaces.
- The force pressing the surfaces together: Higher normal force increases sliding friction.
- The presence of lubricants: Lubricants reduce sliding friction by minimizing surface contact.
In conclusion, sliding friction is smaller than static friction due to the difference in interlocking of surface irregularities when an object is at rest compared to when it is in motion. Understanding this concept is crucial in various fields such as engineering, physics, and material science.