Lesson 6.02 Friction

Types of Friction

There are several types of friction:

• Static friction (occurs when objects are not moving)


• Kinetic fiction (occurs when objects are moving)
  • Sliding friction
  • Rolling friction

Static friction acts on objects that are not moving. It is the strongest type of friction. Imagine pushing your dresser across the room. Initially, it is difficult to get the dresser to move. This is because of static friction.

Once the dresser you're pushing begins to move or slide across the floor, it is much easier to move. This is due to sliding friction. Sliding friction acts on objects that are sliding past each other. Sliding friction is a type of kinetic friction.

Another type of kinetic friction is rolling friction. It acts on objects that are rolling past each other. It is the weakest type of friction. It makes setting objects with wheels into motion easy. Imagine how simple it is to push a toy car across the floor.

→

Cause of Friction

So what causes the friction force? Even when an object seems smooth on the surface, it is actually rough on the microscopic level. This roughness is called microwelds. Microwelds are rough, irregularities on the surface of objects that cause friction to occur. When objects come into contact with one another, their surface roughness causes the friction.

To learn more, watch the video Teachable Moment: Friction (0:33). Login information.

←