Question 1 Why is it difficult to move on wet marble floor?
Question 2 Why is it difficult to walk properly on a well polished floor?
Question 3 What prevents you from slipping every time you take a step forward?
Question 4 What enables us to fix nails in a wall and knots to be tied?
Question 5 Why does a man slip when he steps on a banana peel thrown on the road?
Question 6 Why a pencil will write on paper not on glass?
Question 7 Why climbing a greasy pole is very difficult?
Question 8 Why does a matchstick light when we strike it on rough surface?
Question 9 Why is it difficult to light a matchstick by striking it on smooth surface?
Question 10 Explain how friction enable us to walk without slipping?
Question 11 What enables a car to move on road without skidding?
Question 12 Why it is difficult to drive and control a car on wet road?
Question 13 What enables us to apply brakes and slow down or stop a moving car?
Question 14 What enables a teacher to write on the blackboard with a chalk?
Question 15 What enables us to pick up and hold things in our hands?
Advantages of friction
1)Friction enables us to walk without slipping
We are able to walk on ground because friction between the sole of our shoes and ground prevents us from slipping over the ground.To take a step forward during walking ,we lift one foot Off the ground and push the ground backwards with the other foot.If there were no friction between the sole of our shoe and ground, then our shoe on the ground would slip backwards.Since we push the ground backwards, the force of friction acts in the opposite direction, forward direction, and prevents our foot from slipping backward.
Walking on slippery ground is difficult because the frictional force on slippery ground is much less which may not be sufficient to prevent us from slipping.It is also difficult to walk on well polished floor because the friction on these smooth surfaces is very small.
If a person throws a bucket of water on a smooth marble floor, it would become even more difficult for us to walk on this with marble floor.This is because the friction on wet marble floor becomes very small which cannot prevent us from slipping.
When we accidentally step on a banana peel thrown on the road we usually fall down.This is because the inner side of banana peel being smooth and slippery reduces the friction between the sole of our shoe and the surface of road.And this small frictional force is not enough to prevent our food from slipping backwards.
2)Friction enables a car to move on road without skidding
The friction between tyres of a car and road enables a car to move on road without skidding.When the engine of car makes the wheel of car turn, the tyre pushes the road backwards at its point of contact with the road.The friction between tyre of car and the surface of road acts in the forward direction and prevent it from skidding.Friction provides the forward force which drives the car. If there were no friction between the car tyres and road, then the wheels of car would spin at the same place but the car would not move forward at all the.The car would stay where it was.
It becomes difficult to drive and control a car on the wet road.This is because the presence of water on the surface of a wet road reduces friction and makes it slippery.And because of reduced friction there are more chances of skidding of car.Friction also enables a bicycle to move along a road.All the vehicles are able to move on road because of the presence of friction between their tyres and the surface of road.
3)Friction enables us to apply brakes and slow down or stop a moving car
In a disc brake, a steel disc attached behind each car wheels spins between two small brake pads.When the brakes are applied to the running car by pushing the brake pedal, the brake pads press against the discs of the rotating car wheels.This produce friction between brake pads and the discs, making the wheels to slow down and ultimately stop.
When the bicycle is running , the brake pads of bicycle do not touch the wheels.When we press the brake lever to apply brakes to running bicycle ,then the brake pads rub on the rims of the bicycle wheels.The friction between brake pad and Rim prevents the wheel from moving ahead. Due to this, the running bicycle slows down and finally stops.
If there were no friction then once a vehicle started moving, it would never stop.
4)Friction enables us to write and draw on paper
We are able to write and make drawings on paper because there is friction between the tip of pencil or pen and paper.The pencil has a thin black core made of carbon which is called pencil lead .When we write with a pencil, friction with paper rubs off carbon particles from the pencil lead which sticks to the paper and leaves black marks on paper.
When we write with a pen ,the particles of ink drop off from the pens refill due to friction with paper, stick on the paper and leave marks of writing on paper.
We cannot write with a pencil on a glass sheet because the glass surface is very smooth due to which the friction between the tip of pencil and glass surface is much less.This friction is not sufficient to rub off black graphite particles from the tip of pencil.
A teacher is able to write on the blackboard with a chalk due to friction between the blackboard and Chalk. When the teacher starts to write on the blackboard with a chalk, the rough surface of the blackboard rubs off some chalk particles with sticks to the blackboard and appear as writing on the blackboard.
5)Friction enables us to pick up and hold things in our hands
We are able to pick up book and hold it in our hands due to the friction between the book and the hands.We can hold a glass tumbler in our hands because of friction.
If the outer surface of a glass tumbler is oily all greasy then it becomes more difficult to hold it.This is because the presence of a film of oil on the outer surface of glass tumbler reduces the friction between glass tumbler and our hands.Due to less friction the oily glass tumbler tends to slip from our hand and it becomes more difficult to hold.
It is easier to hold a kulhar in our hands than a glass tumbler.This is because due to the rough surface of the kulhar the friction between Kulhar and our hand is much more which makes it easier to hold it.
Due to the smooth surface of glass tumbler the friction between glass tumbler and hand is much less which makes it comparatively difficult to hold it.
6)Nails can be fixed in a wall due to friction
When we hammer a nail into the wall, it is the friction between the surface of nail and wall which holds the nail tightly in the wall.Without friction ,nails could not be fixed in a wall to hold things.
Friction enables knots to be tied in the strings(ropes).Knots in ropes are held together by friction.Friction enables a person to climb a tree or pole without sliding down all the time.
An oily or greasy pole has much less friction due to which it becomes difficult to climb up a greasy pole.
Friction enables a ladder to be leaned against a wall and do not slip down to the floor.
Friction helps in the construction of building.
Friction enable the belts to drive machines in factories.
7)Friction enables us to light a matchstick
When we rub a matchstick against the left side of a match box ,then friction between the head of matchstick and rough left side of matchbox produces heat. This heat burns the chemical present on the head of matchstick due to which the matchstick lights up.
The matchstick catches fire and starts burning. The burning of a matchstick would not be possible without friction.It is difficult to light a matchstick by striking it on the smooth surface because enough friction is not provided by a smooth surface to produce sufficient heat.
8)We are able to cut wood because there is friction between the blade and log of wood.