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Ncert Exemplar Solutions Class 8 Science Friction
Welcome to NCTB Solutions. Here with this post we are going to help 8th class students for the Solutions of NCERT Exemplar Class 8 Science Book, Unit 12, Friction. Here students can easily find step by step solutions of all the problems for Friction, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.
Friction all Question Solutions :
Multiple Choice Questions :
Question no – (1)
Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play
Answer :
Correct option – (d)
The force of friction comes into play irrespective of whether the objects are solid, liquid or gaseous.
Question no – (2)
In Fig.12.1, a boy is shown pushing the box from right to left. The force of friction will act on the box
Answer :
Correct option – (b)
The force of friction will act on the box from left to right (→)
Question no – (3)
To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?
Answer :
Correct option – (a)
To sharpen the blade of a knife by rubbing it against a surface atone will be the most suitable.
Question no – (4)
A toy car released with the same initial speed will travel farthest on
Answer :
Correct option – (c)
A toy car released with the same initial speed will travel farthest on cemented surface.
Question no – (5)
If we apply oil on door hinges, the friction will
Answer :
Correct option – (b)
If we apply oil on door hinges, the friction will decrease.
Question no – (6)
Which of the following statements is incorrect?
Answer :
Correct option – (d)
Friction does not act on a ball moving through air – This is the incorrect.
Question no – (7)
A boy rolls a rubber ball on a wooden surface. The ball travels a short distance before coming to rest. To make the same ball travel longer distance before coming to rest, he may
Answer :
Correct option – (c)
To make the same ball travel longer distance before coming to rest, he may sprinkle talcum powder on the wooden surface.
Question no – (8)
In a large commercial complex there are four ways to reach the main road. One of the path has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has gravel surface. It is raining heavily and Paheli wishes to reach the main road. The path on which she is least likely to slip is
Answer :
Correct option – (d)
The path on which she is least likely to slip is gravel.
Very Short Answer Questions :
Question no – (9)
Answer :
The second block will need a larger force to move. The second block has a larger mass so it will have larger force of friction.
Question no – (10)
Answer :
Yes, the force of friction acts when rain drops rolls down a glass window pane because two surfaces are meeting each other.
Question no – (11)
Answer :
The boy whose tyres were old and used is more likely to fall on a lubricated road because his tyres are smooth and smoother surfaces offer less friction. So the friction between his tyres and the road is so minimum to allow him a smooth ride.
Question no – (12)
Answer :
As both the boys are applying force of equal magnitude in opposite directions there would be no movement of the box at all hence no frictional force will come into play.
Question no – (13)
Answer :
The ball falling in the tube will not face any frictional force. For a body to face friction it should come in contact with another surface. But the fall is neither facing resistance from air not it is coming in contact with the tube wall so it falling absolutely friction less.
Short Answer Questions :
Question no – (14)
Answer :
When used for a long time the sleepers with rubber soles worn out because of the continuous rubbing of the rubber sole against the floor or road, which makes with worn out.
Question no – (15)
Answer :
Yes, there is force of friction acting between the wheels of a moving train and iron rails. It is a rolling friction because the train wheels are rolling over the iron rails. If a air cushion is introduced between the wheels and the rails the wheels would face less friction than usual.
Question no – (16)
Answer :
During old age when the cartilages wear out it increases the friction between the bones, so an old person faces difficulty in movement of the joints and experience pain in the joints.
Question no – (17)
Answer :
To prevent the rope from slipping off her hands Preeti must increase the friction between her hands and the rope. The two possible ways are wearing some gloves or rubbing some soil from the ground on her hand.
Question no – (18)
Answer :
A rough surface offers more friction than smoother surfaces so a rougher surface is more easy to hold onto and it does not slips away from the hands. The handles of cricket bat or racquet bat are rough to provide firm grip on the bats.
Question no – (19)
Answer :
The Silbatta is etched again and again to make it more rough so that the spices could be ground much more thinner and better.
Question no – (20)
Answer :
The marble will move shortest on the sand surface because sand resist the movement of the marble by applying more friction on the marble whereas on surfaces such as silk cloth and glass it won’t be facing that much friction so it move will to a greater distance.
Question no – (21)
Answer :
They had to apply a larger force to set the car in motion because it was at stationary condition and once it was set in motion it began to roll on the road and the friction between the road and the wheels kept on becoming less and so the duo didn’t need to apply that much of force to keep the car moving.
Long Answer Questions :
Question no – (22)
Answer :
When the knife is sharpened by putting it against the rotating stone sparks often appear at the moment because of the intense that is being produced when the knife is bring rubbed with an intense force for a long period of time. Thus It releases heat in the form of some sparks.
Question no – (23)
Answer :
It is a quite known fact that the more rough a surface is the more friction in will produce. So when the metal sheets is rubbed with a rough sand paper it will create immense friction on the metal sheets so all the impurities or dust particles will be removed from the sheets and eventually it will shine more than the one which was rubbed with a smooth ordinary paper.
Question no – (24)
Answer :
Smoother surfaces offer less resistance to movement so if the rickshaw driver suddenly pulls the brake our body tends to move forward but the seats being too smooth will not create friction against our body. So it often happens that we slip from the seats when the brakes are applied.
Question no – (25)
Answer :
They must put the heavy load on some carriages which have wheels below them. This will reduce their work drastically since they now have to overcome little friction because the wheels will change the sliding friction to rolling friction which requires very little force to overcome.
Other Chapter Solutions :
👉 Crop Production and Management
👉 Microorganisms : Friend and Foe
👉 Synthetic Fibres and Plastics
👉 Materials : Metals and Non-Metals
👉 Conservation of Plants and Animals
👉 Cell-Structure and Functions
👉 Reaching the Age of Adolescence
👉 Force
👉 Sound
👉 Chemical Effects of Electric Current
👉 Light
