Telangana SCERT Class 8 Physical Science Chapter 2 Solution – Friction. Here in this post we provides Class 8 Physical Science Friction Telangana State Board Solution. Telangana State Board English Class VIII Medium Students can download this Solution to Solve out Improve Your Learning Questions and Answers.
Telanagana State Board Class 8 Physical Science Chapter 2 Friction Solution:
(1) What kinds of friction do you know and explain with suitable example?
Ans: – There are four types of friction
Those are –
(i) Static friction
(ii) Sliding Friction
(iii) Rolling Friction
(iv) Fluid Friction
(i) Static friction: – Static friction comes into play when we try to move an object vat rest relative to another surface or object.
In our daily life we observe static friction.
Example like –
(1) A book on a table top
(2) A towel hanging on a rack
(ii) Sliding Friction: – Sliding friction comes into play when an object is siding over another
Examples –
(1) Skis sliding agains snow
(2) Rubbing both hand together to create a heat.
(iii) Rolling Friction: – When one body rolls over the surface of another body the friction offered is called rolling friction.
Example –
(1) Carrying a luggage bag attached with wheels
(2) Moving of cars wheels on road.
(iv) Fluid Friction: – Water and other liquids exert force of friction when objects move through them.
For example – When you observe fluid friction when you travel in a boat. Not only liquids gasses and air also offer friction to bodies like airplanes, Jet, when they move through air.
So, we can say that fluids exert force of friction on objects in motion through them.
(2) A book placed on the surface of a table. The book is pushed in one direction. Draw the forces acting on the book and explain.
Rathe case in horizontal direction, the speed of the book is changing continuously. Its speed is decreasing gradually in the horizontal.
(3) Give few examples for Sliding friction.
Ans: –
(1) Rubbing our hands
(2) Skis sliding against snow.
(3) When some books are pushed from table.
(4) An iron being pushed on any material
(5) An inverter pushed along a floor.
(6) A wheel chair moving on any plane surface.
(7) Any block being slid across the floor.
(4) Explain how does lubrication reduces friction?
Ans: – Lubricants helps us to reduce the friction
When oil, grease or any other lubricants are applied between the moving parts of a machine, a thin layer is formed between the moving surfaces and hence they do not directly sub against each other.
That means if the surface of an object is rough then if we apply lubricants which is smooth, it helps us to reduce the friction.
Interlocking of irregularities is avoided to a great extent by the application of lubricants. Hence movement becomes smooth.
(5) Explain with one example that Frictional force is proportional to the Normal force?
Ans: – Now keep a brick on the horizontal floor and pull it with the spring balance attached to it and measure the frictional force.
Now put another brick over the brick tied to the spring balance or press it vertically with your hand and then measure the force of friction
From these activities you can understand that when you add a brick to the existing brick or apply a force by pressing it vertically. Then the normal force increases and hence you find there is an increase in the frictional force.
So friction is proportional to the Normal force that is
Friction ∝ Normal force
Here ∝ is the symbol representing “Proportional” to.
Application of concepts
(1) Explain why do sportsmen use shoes with spikes?
Ans: – Sportsman uses shoes with spikes because it helps in increasing friction level. So that sportsman can move safely and also sportsman will not slip while he running and it provides better grip. He will be comfortable while playing games.
(2) Would it be easier or difficult for you to walk on a marble floor with soapy water? Why?
Ans: -It would be difficult to walk on a marble floor with soapy water because the friction between floor and our foot is reduced. So it is difficult to walk on floor as soap water will reduce the friction on marble floor.
(3) What happens if we do not reduce friction in machines?
Ans: – If we do not reduce friction in machines they will not able to work properly and smoothly. Because due to friction, they can get heat and could get fire and machines can catch the fine.
(4) What purposes are surved by using bearings in machines? Explain with daily life examples.
Ans: – Bearing in machines are used for easy movement of its parts with very little friction. That’s why it used in machines to reduce friction.
For examples –
(1) Ball bearing are used in cycles.
(2) Bearing also used in paper making machines.
(5) Draw a free body diagram (FBD) to show various forces acting on a body which is sliding on an inclined plane.
Ans: –
F = Friction
N = Normal Force
W = Gravitational Force
F = Frictional Force
Higher Order Thinking Questions
(1) Do you agree with the statement? “Friction is both good and evil.” Explain with examples.
Ans: – The things that will not happen in the world if friction was not present. But I agree with that statement of the surface increases. It means friction can produce heat.
When we try to move a heavy object a lot of energy is wasted to overcome friction.
So that means if there was no friction we can easily push or pull furniture and other things.
(2) Reducing friction to the lowest possible level in machine tools solves the problem of energy crisis and conserve biodiversity. How do you support the statement? Explain?
Ans: – I totally agree with the statement because we know the friction wastes a lot of energy in machines. When more energy is used, we need a lot of coal, petroleum as fuel for burn all this. For this reason environment will get polluted.
Hence, if there is more friction more friction than more pressure will be needed to move the objects. So if we reduce friction, then energy or pressure can be saved and it also helps in conserved biodiversity.
(3) Scientists designed the shape of aeroplane using the technique of reducing fluid friction by observing birds shape. How would you appreciate?
Ans: – It is obvious that when objects move through fluids, they have to overcome friction acting on them. SO efforts are made to minimize friction. For that objects are given special shapes.
This is the reason behind the shapes of aeroplane suing by scientists the technique of reducing fluid friction by observing birds shape.
Because birds have to more about in fluids all the time. Their bodies must have evolved to shapes which would make them not to lose much energy in overcoming friction.
So that aeroplanes wings are look like as birds wings and it also move anywhere to lose much energy in overcoming friction. But by this invention we are able to fly and cover lot of distance in less time.
Multiple Choice Questions
(1) Which material do gymnasts apply on their hands to increase friction
Ans: – c) Coarse substance
(2) The relation between the change the length of spring and the applied force
Ans: – c) Directly proportional
(3) When the speed of the body moving in a straight line changes
Ans: – a) Acceleration
(4) The bodies of birds and fishes must have evolved to shapes which would make them not to loose much energy in overcoming
Ans: – d) Fluid friction
(5) Which of the following friction has self adjusting force
Ans: – b) Static friction
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