Friction class 8 questions and answers: Science Class 8 chapter 9 question answer
| Textbook | Ncert |
| Class | Class 8 |
| Subject | Science |
| Chapter | Chapter 9 |
| Chapter Name | Friction ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Class 8 Science chapter 9 question answer? Now you can download ncert solutions for class 8 science chapter 9 pdf from here.
Question 1: Fill in the blanks.
(a) Friction opposes the ______ between the surfaces in contact with each other.
(b) Friction depends on the ______ of surfaces.
(c) Friction produces ______.
(d) Sprinkling of powder on the carrom board ______ friction.
(e) Sliding friction is ______ than the static friction.
Answer 1:
- (a) Friction opposes the motion between the surfaces in contact with each other.
- (b) Friction depends on the nature of surfaces.
- (c) Friction produces heat.
- (d) Sprinkling of powder on the carrom board reduces friction.
- (e) Sliding friction is lesser than the static friction.
Question 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
Answer 2: (c) static, sliding, rolling.
Question 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.
Answer 3: (a) wet marble floor, dry marble floor, newspaper and towel.
Question 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.
Answer 4: When book slides down on the desk, a frictional force acts between the book and the surface of the desk. The direction of the friction force on the book is opposite to the direction of its motion and acts in an upward direction. It is shown in the diagram below.
Question 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?
Answer 5: The layer of soap makes the floor smooth due to which the friction is reduced. This makes the floor slippery and the foot cannot make a proper grip on the floor. Therefore it is difficult to walk on a soapy floor. We may slip on the floor.
Question 6: Explain why sportsmen use shoes with spikes.
Answer 6: Spikes present on the shoes make the surface of the shoes rough. This increases the friction. As friction increases, the grip on the ground increases. This makes it easier for them to walk or run.
Question 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?
Answer 7: Seema will have to apply larger force since she will experience more frictional force because heavy object will be pressed hard against the opposite surface and produces more friction.
Question 8: Explain why sliding friction is less than static friction.
Answer 8: Friction arises when surface imperfections between two things come into contact and become entangled. There is very little time allotted for slides to interlock. Interlocking is therefore weak. Consequently, less effort is needed to release this entanglement. Sliding friction is therefore less than static friction.
Question 9: Give examples to show that friction is both a friend and a foe
Answer 9:
- Friction as friend:
- We are able to walk because of friction.
- Friction between the tip of the pen and a paper allows us to write.
- Friction as foe:
- Tyres and soles of shoes wear out because of friction.
- Friction between the different parts of machines produces heat. This can damage the machines.
Question 10: Explain why objects moving in fluids must have special shapes.
Answer 10: The objects moving in fluids must have a special shape to overcome the fluid friction acting on them. Efforts are therefore made to minimise the friction, so objects are given special shape having pointed fronts with little broader middle portion which gets tapered at the back called streamlined.