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We encounter different types of friction in our daily lives – from burning a matchstick to writing on a paper. Friction produces heat and sound when there is relative motion between two objects. Friction is the resistive force that occurs due to molecular adhesions and roughness of the surfaces. This force opposes every motion of the object it is working on. There are mainly four types including static, rolling, sliding, and fluid friction. This article discusses only the major types i.e. rolling (when an object rolls on the surface) and sliding (when an object slides on the surface) friction. Additionally, the article will explain the difference between rolling and sliding friction.
Rolling Friction
For a moving body, rolling friction can be defined as a force that resists motion when an object, such as a ball or wheel, rolls on a surface. In general terms, it is an adhesive force between the object and the surface. The source of energy dissipation in this type of friction is the inelastic property of the material. During the movement of an object, deformation energy is considerably higher than the recovery energy. Rolling friction is the force per unit weight of the object that rolls on a surface at a constant slow speed. Remember that the object will experience some air resistance till no traction forces or brakes are applied. The cause of rolling friction or rolling resistance is the deformation of the object or surface it is moving on.Sliding Friction
For a moving body, sliding friction can be defined as a force that occurs when two objects move against each other instead of rolling on a surface. In general terms, when walking or writing, resistance to the movement is created. This type of resistance is referred to as sliding friction or kinetic friction. It resists motion when an object is sliding on a surface. The deformation, speed, and roughness of objects in motion affect sliding friction. It is also dependent on the amount of pressure on both the surfaces in contact. Suppose you are moving a chair; the force you apply is opposed by another force. This force here can be taken as sliding friction. Now, if the roughness of the chair is greater, you need to exert less force for its movement.Difference between Rolling Friction and Sliding Friction
- Rolling friction is the resistance created when one object rolls on the surface. In contrast, sliding resistance occurs when two surfaces are slid or rubbed against each other
- The rolling of two surfaces over one another reduces the friction, while the sliding of two surfaces increases the friction. Therefore, the magnitude of the sliding friction is larger than rolling resistance
- The main reason for sliding resistance is interlocking between the surfaces of the objects in contact. In comparison to this, the deformation of surfaces is the cause of rolling friction
- The coefficient of rolling friction is dependent on the radius and toughness of the surfaces. The coefficient of sliding resistance is not dependent strongly on external factors such as radius and toughness
- Rolling friction results in the rolling of a disc or any circular object. However, sliding resistance is associated with the sliding or gliding movement of the object
Examples of rolling friction and sliding friction
A few examples of rolling resistance in our everyday life are as follows:- Rolling a football or tennis ball on the ground
- Movement of the wheels of a bicycle or any other vehicle
- Zorbing
- A pen rolling on a surface
- Skateboarding
- Pulling a heavy cupboard on the floor
- A box sliding on a surface
- A block sliding on the floor
- Erasing on a paper using a rubber
- Sliding down the slides in a park
