# Friction and Its Types

### Types of Friction for Class 4 Science

When two surfaces are in contact the force of friction acts between them. In this concept, the students will understand factors affecting friction.

After reading the concept, students will be able to:

• Discuss about causes of friction.
• Recall the types of friction such as static friction and fluid frictions.
• State the difference between rolling friction and sliding friction.
• Explain how a paraglider experiences an air resistance.
• Demonstrate how streamlined body of fish reduces fluid friction.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

### What Is Friction:

• Friction is a type of contact force.
• When friction occurs, two bodies remain in contact, so friction is a contact force.
• Overall, we can say that friction is a force that comes into play when two surfaces come in contact with each other.
• The force of friction always opposes the motion of an object and reduces its velocity.
• Frictional force always acts from the opposite side of an object’s motion.

Examples:

• A ball rolling on the floor gradually slows down.
• When we stop pedalling a bicycle, it gradually slows down.
• Dragging a chair on the floor.

### Factors Affecting Friction:

Friction mainly depends on two factors—

• The nature of the surfaces—rough surface or smooth surface.
• If the surface is smooth, the force of friction will be less, and if the surface is rough, the force of friction will be more.
• Friction also depends on how hard the surfaces press together.

### Causes of Friction:

Friction happens when two rough surfaces come in contact, and due to their irregularities, the frictional force starts to act at the opposite side of the motion.

### Types of Friction:

Friction can be divided into three types.

1. Static friction:

• It is the type of frictional force that is exerted on an object which is at rest.
• Static frictional force comes into play until an object starts moving.
• A resting object starts moving after overcoming the static friction.

Examples: Pushing any resting object can cause static friction like walking, rock climbing, rubbing hands, etc.

2. Sliding Friction:

• Sliding friction comes into play when the surface of an object slides over the surface of another object.
• Sliding friction opposes the sliding movement of another object.

Examples: Sliding on a sledge, playing on a slide, dragging anything from right to left on the floor.

3. Rolling Friction:

• Such friction exerts when an object rolls over on a surface.

Examples: Movement of a wheel, the friction between a paint roller and the wall.

4. Fluid Friction:

• When an object moves underwater, the fluid exerts friction on the object, called fluid friction.
• To reduce fluid friction, objects should have a streamlined body.

Examples: Fish moving underwater, Underwater submarines.

### Air Resistance:

• When an object moves through the air, the air exerts a resistance force that opposes the object’s motion, which is called air resistance.
• It is also a kind of frictional force.

Examples: Aeroplanes flying, skydiving, paragliding.

### New Words:

Velocity: Speed of an object.

Fluid: A substance that flows.

Streamlined: A body shape that tapers at both ends.

### Did You Know?

• The strength of static friction is the highest, and the strength of rolling friction is the lowest.
• The velocity of a static object in reference to other moving objects is called relative motion.