NCERT Solutions for Class 8 Science Chapter 12 Friction

NCERT Solutions for Class 8 Science Chapter 12 Friction are given below. Here we have provided the best and error-free answers to all the exercise questions that will strengthen your foundation in science. Solving NCERT questions will assist you in grasping the content in the Crop Production and Management chapter in a better way.

In these solutions, we have answered all the intext and exercise questions provided in NCERT class 8 science textbook. NCERT Solutions for Class 8 Science Chapter 12 Friction provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free or can read them online.

Friction Class 8 Science NCERT Solutions

Exercise Questions

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:

(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 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: (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: (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: When a book slides on the writing desk, a frictional force acts between the book and the surface of the desk. The direction of frictional force on the book is opposite to the direction of its motion and acts in upward direction, as shown in the following figure.

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

Answer: 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: Spikes increase friction and give better grip with the ground. It avoids slipping of sportsmen while playing or running.

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: Friction force is directly proportional to mass. Heavier box will put more force on the floor surface as compared to lighter box and therefore will experience more opposite force (friction). Seema will have to apply larger force.

Question 8: Explain why the sliding friction is less than the static friction.

Answer: Friction comes into play when irregularities present in the surfaces of two objects in contact get interlocked with each other. In sliding, the time given for interlocking is very small. Hence, interlocking is not strong. Therefore, less force is required to overcome this interlocking. Because of this reason, sliding friction is less than static friction.

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

Answer: Friction is both a friend and a foe due to following reasons:

Friction act as friend:

• We are able to walk because of frictional forces between ground and our feet.
• We are able to write because of friction between ball point and the paper surface.
• Nails and screws stick to wall surfaces because of friction.
• Lighting a match stick is because of friction between match stick and the side surface of match box.

Friction act as foe:

• Wear and tear of soles of our shoes is due to friction.
• When a tyre deflates, it is difficult to move the vehicle because of increased friction between the tyre and road surface.
• Machines gets heated up because of friction.
• Due to friction, machines and vehicles consumes more fuel and increase maintenance cost.

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

Answer: When a body moves through a fluid, it experiences an opposing force which tries to oppose its motion through the fluid. This opposing force is known as the drag force. This frictional force depends on the shape of the body. By giving the objects a special shape, the force of friction acting on it can be minimized. Hence, it becomes easier for a body to move through the fluid.

NCERT Solutions for Class 8 Science Chapter 12 – A Brief Discussion

CBSE Class 8 Science NCERT Solutions Chapter 12 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 8 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.