Friction and Its Types | Grade 4 Science | Learning Concepts
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Concept: Friction and Its Types

Friction and its features:

  • 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.


  • 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.
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