# Types of Friction

1.What Is Dry Friction?

• The frictional force that comes into action when two solid bodies come in contact with each other is called dry friction.

2.Dhriti Is the Class Monitor. She Is Told to Clean the Blackboard. By Mistake, Dhriti Cleaned the Blackboard With Water. Now the Teacher Cannot Write and Said That She Has to Wait for a Few More Minutes- Why Did the Teacher Say So?

• Friction plays a role while writing on a blackboard or paper.
• The blackboard, when cleaned with water, became smoother, which led to the reduction of friction.
• Since the surface got smoother, the teacher could not write on it with chalk. She suggested waiting as the blackboard would not be as smooth once the water dries off completely.

3.Why Are Two Wheels Attached to This Chair?

• The picture shows a wheelchair used to carry old or sick people.
• This chair needs to be dragged.
• Adding wheels to the chair's base reduces the friction between the chair and the ground and makes it easy to drag the chair.

4.In Which Directions Friction Force and Motion Work, Explain With an Image.

• Motion and friction force act in directions opposite to each other.
• If a vehicle moves towards the east, the frictional force will act in the west.

5.Why Do Aquatic Animals Have Streamlined Bodies?

• Aquatic animals like fish, whales, and dolphins have streamlined bodies.
• Ocean and river water exert fluid friction on the bodies of aquatic animals.
• A streamlined body is tapered at both ends, which helps in reducing friction and hence swimming in a better manner.
• For the very same reason, boats and ships are streamlined in shape.

6.Why Do Aeroplane Wheels Sometimes Show Sparks While Landing on the Runway?

• A runway is made of concrete. When aeroplanes land, their wheels touch the surface of the runway first.
• Due to the high speed of the aeroplane, static electricity is produced as a frictional force acts due to contact between the surface of the wheels and the runway.

7.Reshma Was Running on the Wet Floor, and Suddenly She Slipped. Why Do You Think It Happened?

• Friction helps us to stand, run or walk on the floor.
• Due to wetness on the floor, the friction gets reduced, which may lead to slipping or difficulty in walking or standing.
• Reshma slipped on the wet floor due to reduced friction because of the presence of water.

8.Identify the Types of Friction in the Following Images.

1. Static friction.
2. Sliding friction.
3. Sliding friction.
4. Fluid friction.