Friction

The characteristics a force-displacement graph of a spring is a direct one.

Explain the characteristics of a force-displacement graph of a spring.

Are there any disadvantages for friction? If yes, list few disadvantages of friction.

How is the irregularity of a surface and the friction related? Explain.

Look at the pictures given below and tick below the one(s) that will reduce friction.

You skid a lot more while you are wearing socks. Why?

Why do you think we slip on a banana peel?

Why do tyres of vehicles wear out?

A matchstick gets lighted due to friction between which two objects?

Take a book. Keep it on the floor and push it with your finger. Now keep $3-4$ or more pencils under the book in a vertical position. Now push the book. Is less effort required to push the book? What do you feel is the reason behind it?

Take a book. Keep it on the floor and push it with your finger. Now keep $3- 4$or more pencils under the book in a vertical position. Now push the book. 
Is less effort required to push the book?

What are the conditions that cause friction?

_____  (Talcum powder/Sand) is sprinkled on the carrom board to reduce friction.

Oil applied to a surface to reduce friction better serves as a :

Give reasons. 
Friction is both a friend and a foe. 

Friction is not a force.

Smooth surfaces have more friction than rough surfaces. 

Streamlined body helps in reducing the amount of fuel a vehicle uses. 

Heat can be produced in various parts of the machines due to friction. 

Friction acts in a direction opposite to that of the movement of an object.