Rolling Friction: Introducing the Weakest Friction to Students.

June 05, 2019

Rolling Friction: Introducing the Weakest Friction to Students.

Why is rolling friction weaker than other types of Friction? Students tend to confuse how an increase and decrease in friction affects motion. Hands-on discovery is the best way to help ease this confusion.

What is Friction?

Friction is a force that will hold back the movement of an object. It is the force that is opposing motion between any objects that are in contact. Friction is in the opposite direction of the object that wants to or is in motion. It is referred to as the resistance force. The key is to get your students to understand friction by thinking about the resistance force and effort needed to move the object.

Why is rolling friction weaker than the other types of friction?

The four types of friction are static friction, sliding friction, rolling friction, and fluid friction. Static friction is the strongest because it is what keeps an object in place. Since objects are not moving the forces are balanced. A greater force must be introduced to cause the object to move. In sliding friction the objects are sliding against each other. The resistance force is trying to stop the object. The object has a harder time overcoming the resistance force when sliding. Rolling friction is weaker because basically, it is rolling. The rolling motion or cyclical motion allows it to move, change direction, or change speed more easily. Rolling something is better at overcoming the resistance force. Less effort is needed to move an object that has wheels than a flat object. Fluid friction is when solids try to move through a fluid (gas or liquid). This type of friction is hard to compare to rolling friction but is definitely stronger.

Focus On

The key to helping students understand this concept is to perform a hands-on lab before introducing concepts and vocabulary. This will allow them to build knowledge and see friction in action. After the lab students should focus on the forces involved and not just objects coming into contact with each other. They need to learn that an increase in friction is an increase in the resistance force and a decrease in friction is a decrease in the resistance force. When there is an increase in friction the effort to move the object will increase. When there is a decrease in friction the effort to move the object decreases. Make sure to introduce the term resistance force. Ask the students which surface has an increase in resistance force? How does that affect the amount of friction? I have found many students think an increase in friction means that the object can more easily more. When you add in the concept of resistance force it makes more sense that the object will not move as easily.