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Chapter Analysis
Intermediate10 pages • EnglishQuick Summary
The chapter on friction in class 8 science explores the fundamental concepts of friction as a force that opposes motion between contact surfaces. It discusses the factors affecting friction, such as the nature and smoothness of the surfaces, and differentiates between static, sliding, and rolling friction. The chapter also explains the practical applications and disadvantages of friction, and the methods to reduce it using lubricants and by streamlining shapes to minimize air and fluid resistance. Additionally, it highlights the importance of friction in everyday activities and industrial applications.
Key Topics
- •Causes of friction
- •Static, sliding, and rolling friction
- •Factors affecting friction
- •Advantages and disadvantages of friction
- •Methods to reduce friction
- •Concept of drag in fluids
- •Applications of friction in daily life
- •Streamlining to reduce fluid friction
Learning Objectives
- ✓Understand the concept of friction as a force opposing motion.
- ✓Differentiate between types of friction: static, sliding, and rolling.
- ✓Identify factors that affect the magnitude of friction.
- ✓Explore practical applications and implications of friction.
- ✓Learn methods to increase or decrease friction as required.
- ✓Understand the role of friction in fluid dynamics.
Questions in Chapter
Fill in the blanks: (a) Friction opposes the _____________ between the surfaces in contact with each other.
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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.
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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
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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.
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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?
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Explain why sportsmen use shoes with spikes.
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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?
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Explain why sliding friction is less than static friction.
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Give examples to show that friction is both a friend and a foe.
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Explain why objects moving in fluids must have special shapes.
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Additional Practice Questions
What is the effect of surface roughness on friction?
mediumAnswer: Surface roughness increases the interlocking between two surfaces, thereby increasing the frictional force.
Describe how lubricants help in reducing friction.
easyAnswer: Lubricants create a thin layer between surfaces, reducing the direct contact and interlocking, thus decreasing friction.
Why is friction considered a necessary evil?
mediumAnswer: Friction is necessary as it allows us to walk, write, and drive safely. However, it also causes wear and tear, leading to energy loss as heat.
How does the shape of an object affect fluid friction?
mediumAnswer: Streamlined shapes minimize fluid friction by allowing smoother flow of air or water over the surfaces, reducing drag.
What role does friction play in braking a vehicle?
mediumAnswer: Friction between the brake pads and wheels causes the vehicle to slow down and eventually stop by converting kinetic energy into heat.
Explain how ball bearings reduce friction in machines.
easyAnswer: Ball bearings replace sliding friction with rolling friction, which is significantly lower, allowing smoother movement of machine parts.
Why do athletes wear spiked shoes?
easyAnswer: Spiked shoes increase friction with the ground, providing better grip and preventing slipping during activities.
Illustrate how friction can be useful in everyday life.
mediumAnswer: Friction allows us to hold objects, control motion in machines, and walk without slipping.
Discuss the ways to increase friction when it is desirable.
easyAnswer: Grooving surfaces, using non-slip materials, and applying brake systems can increase friction where needed.
How does fluid friction affect moving objects over time?
mediumAnswer: Fluid friction, or drag, opposes motion and causes energy loss over time, slowing down the object.
NCERT Exemplar
AvailablePractice with NCERT Exemplar problems and solutions for this chapter. Exemplar problems are designed to help you master the concepts with advanced-level questions.
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