NCERT Solutions Class 8 Science Chapter 12 Friction
NCERT Solutions Class 8 Science Chapter 12 Friction: National Council of Educational Research and Training Class 8 Science Chapter 12 Solutions – Friction. NCERT Solutions Class 8 Science Chapter 12 PDF Download.
NCERT Solutions Class 8 Science Chapter 12: Overview
NCERT Solutions Class 8 Science Chapter 12 – Friction
CHAPTER: – 12.
1) Fill in the blanks.
(a) Friction opposes the __relative motion__between the surfaces in contact with each other.
Explanation- (According to the characteristics of the frictional forces it always opposes the force applied when traveling on the surface.)
(b) Friction depends on the ___smoothness__________ of surfaces.
Explanation- (The surface will be smootherthan the frictional force also needed less)
(c) Friction produces __heat________.
Explanation- (The two surfaces after meeting produces the temperature)
(d) Sprinkling of powder on the carrom board __reduce___ friction.
Explanation- (This powder makes the surface smooth then it becomes friction less).
(e) Sliding friction is ____less_______ than the static friction.
Explanation-(The sliding is works on a rolling body which always less than the static friction)
2) Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below.
Choose the correct arrangement.
(a) rolling, static, sliding
(b) rolling, sliding, static
(c) static, sliding, rolling
(d) sliding, static, rolling.
Ans: – Option (c).
3) Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
(a) wet marble floor, dry marble floor, newspaper and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor.
(d) wet marble floor, dry marble floor, towel, newspaper.
Ans: – Option (a).
Explanation- How much the surface will be smooth the friction will be less. In the case wet marbles are sleepier.
4)Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Ans:- When the desk is tilted then the book start sliding down because of the frictional forces acting on it. This frictional force acting in parallel to the line of the table in which direction it tilted and in the opposite direction as well.
5)You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Ans: – As when we spread the soapy water on the surface of the marble the force of friction become less. As a result, we see the sliding is happening in the marbles when we step on it. The more friction presents the more we get help in walking.
6)Explain why sportsmen use shoes with spikes.
Ans: – The sportsman when uses the shoes with the spike then the friction is increases. And we know for the movement or running the frictional force makes it easier so, this spike helps in running with great frictional forces.
7) Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Ans: – As lighter box created the less frictional force as compared to the heavier boxes. So, when Seema will push the heavier box in the same frictional surface apply more forces to move. The more weight creates more friction.
8)Explain why sliding friction is less than static friction.
Ans: – The friction is nothing but the interlocking between the two surfaces. So, when the both surface faces each other then the friction is produces for sliding friction this force is less because of the less time of attraction between the surfaces.
9)Give examples to show that friction is both a friend and a foe.
Ans: – The nature of friction as a friend is seen when we write something on the paper. This frictional forces between the pen with the paper makes it easy to write.
And the friction works as foe when there happen damaged because of the creation of high temperature because of the attraction of two surface.
10)Explain why objects moving in fluids must have special shapes.
Ans: – The frictional force of the fluids which is the main reason behind the passing of object through the rivers, lake or sea. This frictional force depends on structure of the object as the structure is the reason behind the less friction in the fluid. As a result of that wee see the submarine in the sea is like different shape as ship in the sea.