NCERT Class 8 Science Chapter 12 Friction

NCERT Class 8 Science Chapter 12 Friction Solutions to each chapter is provided in the list so that you can easily browse through different chapters NCERT Class 8 Science Chapter 12 Friction and select need one. NCERT Class 8 Science Chapter 12 Friction Question Answers Download PDF. NCERT Class 8 Science Solutions.

NCERT Class 8 Science Chapter 12 Friction

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 8 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 8 Science Chapter 12 Friction and Textbook for All Chapters, You can practice these here.

Friction

Chapter: 12

NCERT TEXT BOOK EXERCISES

Q. 1. Fill in the blanks:

(a) Friction opposes the _________  between the surfaces in contact with each other.

Ans. relative motion.

(b) Friction depends on the _________ of surfaces.

Ans. nature.

(c) Friction produces __________.

Ans. heat.

(d) Sprinkling of powder on the carrom board __________ friction.

Ans. reduces.

(e) Sliding friction is _________ than the static friction.

Ans. less.

Q. 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. (c) static, sliding, rolling.

Q. 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. (a) wet marble floor, dry marble floor, newspaper and towel and little.

Q. 4. Suppose your writing desk is tilted a little. A book kept on it starts sliding. Show the direction of frictional force acting on it.

Ans. The book moves downwards. The frictional force is acting opposite to the movement of book. So it acts upwards.

Q. 5. You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why?

Ans. It is difficult to walk on a soapy floor because layer of soap makes floor smooth. The coating of soap reduces the friction and the foot cannot make a proper grip on the floor and it starts getting to slip on the floor.

Q. 6. Explain why sportsmen use shoes with spikes.

Ans. Sportsmen use shoes with spikes to increase the friction so, that their shoes do not slip while they run or play.

Q. 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. The heavy object will be pressed hard against the opposite surface and produces more friction. So Seema will have to apply a larger force due to excess friction.

Q. 8. Explain why sliding friction less than static friction.

Ans. Sliding friction is always less than static friction because two sliding objects find less time to get interlocked against each others, irregularities of surfaces so they get less friction.

Q. 9. Give examples to show that friction is both a friend and a foe.

Ans. Examples to show that friction is a friend.

(i) It allows us to walk comfortably on ground.

(ii) It allows us to grip and catch different objects.

(iii) Things don’t move from their places because of friction.

(iv) Speeds of moving objects can be minimized or stopped by friction only.

(v) It helps us to write on paper or black board.

Examples to show that friction is a foe:

(i) Friction causes wear and tear in objects.

(ii) Regular maintenance of objects moving against each other (machine and tools) wastes a lot of useful money.

(iii) It makes the movement of heavy objects very difficult.

(iv) It causes damage the parts of machines.

(v) It does not allow the free movement of objects.

Q. 10. Explain why objects moving in fluids must have special shapes.

Ans. The object moving in fluids must have a special shape. This type of shape is called streamlined shape. The streamlined shape helps to overcome the friction between objects and fluids. The objects have pointed fronts with little broader middle position which  gets tempered at the back.