Category: Physics Notes PPT

An equinox meaning is an event in which a planet’s subsolar point passes through its Equator, and the day and night remain of equal length. Equinoxes appear when both the Northern and Southern Hemisphere experience roughly equal amounts of daytime and nighttime. Regarding the equinox solar system, either of the two points presents in the sky where the Sun’s annual pathway- ecliptic and the celestial equator interest. Multiple ancient monuments mark the equinoxes, like the Hindu temple complex Angkor Wat in Cambodia, situated at the spot where the Sun rises directly above its central temple. 

Two equinoxes occur-  Autumnal and the Vernal Equinox. The autumnal equinox falls on September 23, when the Sun crosses past the celestial equator going south. The Vernal equinox occurs on March 21, which marks the beginning of spring in the Northern Hemisphere. This is a typical equinox example. 

Equinox Space Definition

Equinox space definition occurs where the day and night are almost of the same length and occurs twice a year in both the Northern and Southern Hemispheres. This phenomenon is known as Equinox, meaning equal parts, derived from the Latin words’ aequus’, which means equal, and ‘nox’, which means night. Equinoxes are historic insignia of seasonal change.

What Causes an Equinox?

The Earth orbits the Sun at a tilt of about 23.5 degrees, leading to different parts of our planet receiving more or less of the Sun’s radiation at various times of the year, depending on the planet’s position in its orbit. All countries witness the Sunrise in the East and set in the West. However, the Sun also moves to the North for half the year and South the remaining half time of the year. This depends on where the country is located. 

The Northern Hemisphere experiences a more extended period of daylight, while the Southern Hemisphere experiences shorter sunlight periods around July. Around the time of December, the vice-versa occurs. However, twice a year- March and September, the Earth’s tilt aligns with the orbit around the Sun.

At this time of the year, the Sun is directly overhead above the equator, and both the Northern and Southern Hemispheres get the same hours of daylight and night. The line that divides the day and night during an Equinox is known as the ‘grey line’ or ‘twilight zone’, and this line bisects the Earth through the South and North poles. 

During an Equinox in the solar system, the Earth gets a few more minutes of light over darkness. Sunrise occurs when the Sun’s tip edges over the horizon, and sunset is when the Sun’s end disappears over the other edge under the skyline. 

Equilux is also known as ‘equal light’; it’s used when the day and night are exactly equal because of how Sunrise and sunset are defined. The phase of equilux occurs a few days before the spring equinox and a few days after the autumn equinox.

When Do Equinoxes Occur?

Equinoxes do not necessarily occur on the same day each year. Instead, the Equinox occurrences happen during the spring of March 20 and the fall of September 23. These shifting dates are because the Earth’s year is not exactly 365 days as there happens to be an extra quarter of a day with approximately 6 hours that accumulates each year. This disruption causes the date of the Equinox to shift to two different time frames of the year. The Earth’s orientation towards the Sun also constantly moves, tweaking the timing of the Equinox.

The Equinoxes mark the beginning of two seasons- Spring and Autumn, depending on the Hemispheres- Northern or Southern. However, the meteorological start of these two seasons is March 1 and September 1, respectively.

In the Northern hemisphere, the March equinox heralds the beginning of the Spring season, and the phase is known as Vernal or Spring Equinox. The term ‘vernal’ comes from the Latin word ‘ver’, meaning spring. Simultaneously, the Southern hemisphere shifts to experience Autumn. The converse is true in September when the Northern half descends into Autumn’s cold wintertime, the Southern half experiences Spring.

Earth is not the only celestial body that experiences equinoxes. In fact. Every other planet in the solar system holds equinoxes when the planet’s orbit and tilt align with the Sun resulting in both the hemispheres receiving roughly equal amounts of light and darkness. 

Vision is one of the most precious gifts that has been given to us by nature. The human eye is one of the five senses possessed by human beings and it is a part of the sensory nervous system, the eye reacts to light and helps humans achieve their vision. There are various accessory organs in the human eye, like the pupil, lens, retina, cornea, iris, etc. All the accessory organs of the eye work in synergy for humans to achieve their sense of vision. The human eye can see both nearby and distant objects but the working mechanism is different in both cases.  When we are looking at distant objects, the rays diverge and become parallel when they reach the eye, so to see distant objects, the concave eye lens is required because it has a large focal length, and it’s thick too. But when we are looking at nearby objects, the object rays diverge when it reaches the eye. In this case, the convex eye lens of high converging power and short focal length is required.

Most Common Eye Defects

Eye defects are a major health hazard in these times, it can be defined as the disability of ciliary muscles, these ciliary muscles are pivotal for the changing of the shape of the eye lens. The disability of the ciliary muscles can cause problems regarding image formation of any object in the retina and can lead to the defect of vision. The three most common types of eye defects seen in humans are:

• Nearsightedness or Myopia – In which distant objects are not seen clearly.

• Farsightedness or Hypermetropia – In which Nearby objects are not seen clearly.

• Presbyopia – It is generally seen in elderly age groups in which distant as well as nearby objects, both are not seen clearly.
  

What is Myopia?

When a person is not able to see distant objects clearly until the object is kept closer to the eye, it is stated as myopia. Myopia is also called nearsightedness or short-sightedness. All the nearer objects are clearly visible to myopic patients. Two issues usually cause myopia; they are:

When the image is formed in front of the retina, the person is not able to see distant objects clearly, and this happens because of the high convergence of the eye lens. 

And in the second case, that is when the eyeball gets too elongated, the retina then gets distant from the eye-lens. Over here, the eye lens has good converging power, but then also the image gets formed in front of the retina.

Because of myopia, the person gets blurry vision while driving. This defect can develop in childhood and can grow gradually or rapidly depending upon the power of the eye.  

This eye defect is overgrowing, and the most common symptoms are eye strain, fatigue, headache, and squinting. Myopia usually occurs when a person reads a book or computer closely. This can even happen to any individual who spends less time outdoors. 

How is Myopia Corrected?

If a person has nearsightedness or short-sightedness, then they are asked to wear spectacles, including a concave lens. 

A concave lens is used to treat myopic eyes because the lens diverges the parallel light rays coming from distant objects. Hence the virtual image is formed at a distant point of the myopic eye. 

And now, as the light rays are at the proper distance, the objects can be easily focused by the lens, and the image is thus formed on the retina. In simpler words, the concave lens decreases the converging power.

A myopic eye can also be treated by a refractive survey or by contact lenses. Although refractive surgeries are costly, it gives good results in the end. There are different degrees of myopia. 

The formula for calculating the power of the concave lens for correcting myopia is: 

1/image distance (v) – 1/object distance (u) = 1/focal length (f) i.e., (v-u)/f. 

Myopia Defect and Blindness

Myopia is a severe defect and can aggravate under extreme circumstances. There is a stage when myopia is at its peak, and this stage is called degenerative nearsightedness or high myopia. Although this stage is quite rare, once reached at this stage, it becomes impossible for a person to retain normalcy, and they can lose their eyesight.

The most serious complication seen in the myopic patient is cataract, retinal detachment, and glaucoma. The seriousness can be further divided into: pathological myopia, and degenerative myopia.  Among these three issues, the one which can lead to blindness is retinal detachment.

Conclusion:

The Human eye is a very sensitive organ, it has a very advanced mechanism where the human eye and its organs work in tandem with the nerves of the human mind to help with the process of image formation. There should be proper care taken of the eyes as it is the most significant sense which is necessary for our daily functioning. People who use phones and laptops for a long duration of time should use blue screens and spectacles which protect them from radiation.

Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are pyroelectric, with the additional property that their natural electrical polarization is reversible. The term is employed in analogy to ferromagnetism, during which a cloth exhibits a permanent moment of a magnet. Ferromagnetism was already known when ferroelectricity was discovered in 1920 in Rochelle salt by Valasek. Thus, the prefix Ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. Materials that are both ferroelectric and ferromagnetic are known as multiferroics. 

Examples of Ferroelectric Materials Include: 

Ferroelectric Compound Polarization

When most of the materials are polarized, the polarization induced, which is denoted as P. It is almost exactly proportional to the applied external electric field E. Thus the polarization is a linear function. This type of polarization is called linear dielectric polarization. 

Some materials are also known as paraelectric materials, These materials sometimes show a more enhanced nonlinear polarization. Whereas the electric permittivity, such as the slope of the polarization curve, is not constant as compared to that of the linear dielectrics but it may be a function of the external field.

In addition to being nonlinear, the ferroelectric materials demonstrate spontaneous nonzero polarization even in the application of the electric field E. The different feature of ferroelectrics is that the spontaneous polarization can be reversed by applying a suitable strong electric field within the opposite direction. Therefore the polarization is dependent not only on the present field but also on its history, which yields to a hysteresis loop. They are called ferroelectrics by analogy to ferromagnetic materials, which have spontaneous magnetization and exhibit similar hysteresis loops.

Typically, these materials demonstrate the ferroelectricity only below a particular phase of change of temperature, this change is called the Curie temperature and denoted as TC. These materials are paraelectric above this temperature, thus the spontaneous polarization vanishes, and therefore the ferroelectric crystal transforms into the paraelectric state. Many ferroelectric materials lose their piezoelectric properties completely above the Tc. Because the paraelectric phase of these materials has a centrosymmetric crystal structure.

Ferroelectric Properties

There are two types of properties that are exhibited by the ferroelectric compounds: 

1. Pyroelectric Properties and Spontaneous Polarisation: 

All ferroelectric materials are pyroelectric in nature, however pyroelectric materials are not ferroelectric. Below a transition temperature called the Curie temperature, the ferroelectric and the pyroelectric materials are polar and possess an electric dipole moment that is also known as spontaneous polarization. But this polarity can be re-oriented or reversed partially or fully by the application of an electric field with ferroelectric materials. Complete reversal of the spontaneous polarization is known as “switching”. The non-polar phase that can be encountered above the Curie Temperature is known as the paraelectric phase.

The direction of this spontaneous polarization conforms to the crystal symmetry of the material. While the re-orientation of the spontaneous polarization occurs as a result of atomic displacements. The magnitude of the electric dipole moment is greatest at a temperature below the Curie temperature and approaches zero as the temperature is nearer to the Curie temperature.

2. Piezoelectric Properties: 

Due to the reason that all the pyroelectric materials are piezoelectric, this means that the ferroelectric materials are inherently piezoelectric. This means that in response to an applied mechanical load, the material is capable of producing an electric charge that is proportional to the load. Similarly, in response to the applied voltage, the material will produce a mechanical deformation.

Properties including the piezoelectric, dielectric, and electro-optic coefficients may vary by several orders of magnitude in the narrow temperature band around the Curie temperature. Especially the changes to these coefficients are much more gradual when these are compared to other temperature ranges. The piezoelectric coefficient is much greater in the region of CT. Other properties such as dielectric strength and electro-optic properties also change more markedly in the region of the Curie temperature when compared to other temperature ranges.

Ferroelectricity Applications

• The nonlinear nature of the ferroelectric materials is often required for the purpose to make capacitors with adjustable capacitance. Typically, a ferroelectric capacitor simply consists of a pair of electrodes that are sandwiching a layer of ferroelectric material. The permittivity of these ferroelectrics is not only adjustable but is commonly also very high. This happens especially when the phase of the temperature changes. Because of this reason, the ferroelectric capacitors are small in physical size when compared to dielectric capacitors of comparable capacitance.

• The spontaneous polarization of ferroelectric materials, when plotted on the graph, leads to a hysteresis effect which may be used as a memory function. Ferroelectric capacitors are sometimes required to make ferroelectric RAM that is used for computers and RFID cards. In these applications, a thin film of ferroelectric materials is typically used. Due to the reason that this allows the required field to switch in between the polarization that has to be achieved with a moderate voltage. However, while using thin films an excellent deal of attention must be paid to the interfaces, electrodes, and sample quality for devices to figure out the reliability.

• Ferroelectric materials are piezoelectric and pyroelectric. These combined properties of piezoelectricity, memory, and pyroelectricity make the ferroelectric capacitors very useful for example in sensor applications. Ferroelectric capacitors are utilized in medical ultrasound machines, top-quality infrared cameras, in different sensors such as vibration sensors, fire sensors, sonar, and even in the fuel injectors on diesel engines.

• The recent interest is the ferroelectric tunnel junction (FTJ) during which a contract is formed by a nanometer-thick ferroelectric film that is placed in between the metal electrodes. The thickness of the ferroelectric layer is enough to permit the tunnelling of electrons. The piezoelectric and the interface effects are also because the depolarization field may cause an enormous electroresistance (GER) switching effect.

• The catalytic properties found in ferroelectrics have been studied since 1952. It was observed by Parravano, in the anomalies of oxidation rates of CO over the ferroelectric sodium and potassium niobates near the Curie temperature of those materials. The surface-perpendicular component of the ferroelectric polarization can dope polariz
  ation-dependent charges on the surface of the ferroelectric materials. This opens the possibility of performing catalysis beyond the limits of the Sabatier principle. On the other hand, ferroelectric polarization-dependent chemistry can offer the possibility of switching the surface of adsorbate interaction from strong adsorption to strong desorption. Hence a compromise between desorption and adsorption is not needed. Ferroelectric polarization can also act as an energy harvester. 

Conclusion

Energy harvesters convert various energy sources to electrical energy. Ferroelectric polarization can have an important role to increase the output power of energy harvesters by enhancing internal potential. Strong ferroelectric polarization produces high piezoelectric potential and surface potential. 

There are different types of motion related to the human body. Do you know what causes and obstructs motion in the body or object? The answer is the application of force. In general physics, the term force and motion are interrelated and are two sides of the same coin. For example, the interdependence of force and motion can be viewed from the perspective of throwing a ball and catching it back. A force causes interaction between two or more bodies and when that remains unobstructed generates a change in the state of motion. To figure out this relationship existing between force and motion we have to understand the terms individually. 

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What is Force? 

To comprehend what is force, we have to think in terms of pull and push. The push and pull acting on an object or energy as a movement or attribute of physical activity is defined as forced. 

Similiar to push and pull, words like squeeze and stretch also explains the concept of what forces can do. This mainly happens when two entities come in contact. Based on Newton’s universal law of gravitation every object in this universe exerts a force on other objects.  

What is the S.I. unit of Force?

If you want to know what is the S.I. unit of force, we have to know about Sir Issac Newton who first studied gravity and force. So, it is obvious what is the unit of force. It is called the Newton.

F = ma

1 Newton = 1 kg x 1 m/s2

What is Force Measured in? 

These are the units of force that explain how force is measured. 

• This is a standard international system of a unit (SI unit) which is expressed in Newton (N).

• There is a centimetre gram second system of a unit (CGS unit) which is expressed in dyne.

• There are other units like pound-force, kip, poundal, kilopound. 

What are the Different types of Force?

There are two fundamental types of forces that exist:

1.  Contact forces

2.  Non-contact or action-at-distance forces

Now let us understand these types of forces and their subtypes in some detail.

A force that is exerted on an object or body directly through being in contact with it or being in contact with its medium is known as contact forces. The various types of contact forces are:

1. Muscular forces- Have you ever seen a bodybuilder lift weights or a person pushing his broken car? Both of them do so by applying what is known as muscular forces. As the name suggests, this is the type of contact force in which the muscles are used to exert force on another object to bring it in motion, lift it, change its shape or size, make it stop, or make it move faster or slower.

2. Frictional forces- Every object in motion has a frictional force acting on it. It can be described as a force that causes resistance between the surface of the object in motion and the surface it is moving on. When you light a matchstick or apply brakes to a moving vehicle frictional force is present between the surfaces of both objects, which induces fire in the matchstick and stops the vehicle from moving.

3. Normal force- An object lying on a flat surface can seem to be still but in reality, some forces are acting on it. The force of gravity and the atmosphere act on the object to make it absolutely still. It is called a normal force.  

4. Applied force- Applied force is simply the force that is applied by someone on an object to make it move in different directions.

5. Tension force– It is the type of force that is transferred through a cable, wire, rope, or any similarly long object that is anchored to another object. It creates tension between both the objects exerting the same pressure on both of them.

6. Spring force- As the name suggests, this is the type of force that is induced through a spring- compressed or stretched – onto another object to either push or pull it.

7. Air resisting force- Frictional force that is exerted by the air on an object is called air resisting force. Aeroplanes, birds, kites, and other types of flying objects in the air experience this.

The force that is exerted on an object without the object being in contact with anything is known as non-contact forces. The different types of non-contact forces are-

1. Gravitational force- The Earth has a gravitational force that attracts all the objects and substances of Earth towards it. There is no contact between the object and the gravity, yet this force is exerted.

2. Magnetic force- Magnets exert different amounts of force on different objects and this force is called the magnetic force.

3. Electrostatic force- Similar to magnets, electrically charged bodies also induce a certain amount of force on different objects which are called electrostatic forces.

What is Motion?

We can define what is motion in simple words regarding the change of position of the body to time. A train moving, water flowing from the tap, boy walking, etc., all exhibits the state of motion. The act of breathing is also defined as motion. Therefore, every physical process that we experience in this universe is composed of some or other sort of motion. Neither a motion can be swift, nor it can be slow. All this explains what is the meaning of motion. It is vital to understand the concept of motion because it has relevance in the physical world. 

What is the meaning of Motion?

Various terms help us to describe further what is motion in the actual sense. It includes distance, displacement, time, and speed. With terms like displacement and distance, we can describe a change in position. Distance is not easy to explain since it depends upon the path that one has taken. On the contrary, displacement is an easier concept because it always gives a definite answer. It is the shortest distance covered between the two points. If the motion is in the straight line, distance and displacement will be the same. If the motion is not in a straight line, the distance always tends to be greater than the displacement. 

The Relation between Force and Motion

Force and motion are deeply interconnected with each other. What force can do is produce motion in an object or body. For instance, an object is moving and we can say that a force is acting or must
have been acted upon to cause the state of motion. When force is applied, it changes the position of the object concerning time resulting in motion. The motion, in other words, is described as a change in speed or change in direction. Isaac Newton was the first to discover the relation between force and motion. He came to three conclusions: 

• Force can accelerate the object. 

• Force can decelerate the object. 

• Force can cause a change in the direction of the object. 

Did you Know?

Force has a different effect on the object or body. These are listed below:

• Force application can make a body at rest move.

• Force can accelerate or decelerate the speed of a moving body.

• Force can completely stop a moving body.

• Force can also change the direction of a moving body

• Force can transform the shape and size of a body.  

Force and motion are the prime concepts of physics that students have to learn and understand at the basic level. This foundation of knowledge will aid them to grab hold of the advanced conceptual topics in higher classes. 

Everything present on Earth can be categorized into major subsystems, which are water, air, living things, and land. These are termed spheres. To be more precise, they are known as:

In the following segment students will get a more precise idea about each of the subsystems and how do Earth’s spheres interact with one another? 

How do Spheres Interact with Each Other: Earth’s Subsystems

1. Hydrosphere

The hydrosphere of the Earth is an umbrella term for every waterbody like oceans, lakes, rivers, moisture, and underground aquifers. It can be any state of water– solid, liquid, and gaseous. Experts suggest that the entire hydrosphere ranges around 1.3 billion cubic kilometers.

Oceans comprise above 97% of the water on Earth, and the remaining portion is freshwater. Again from this freshwater portion, two-thirds remain frozen in the mountains and poles. You must note that although water covers a considerable part of the planet, it holds only 0.023% of Earth’s mass.

Our Earth’s environment is not static, and hence water modifies its form according to the different stages of the hydrological cycle. First, water is collected through rains; then it goes underground, again rises up in the way of springs, and flows into rivers, lakes, seas, etc. Also, from these streams, water gets evaporated, and the cycle continues.

2. Atmosphere

Earth’s atmosphere comprises all the gasses on Earth that are held by its gravitational pull. Air contains 97% nitrogen, 21% oxygen, and the left portion includes carbon dioxide, argon, and other gasses.

The atmosphere can be further classified into four different zones, namely – troposphere, stratosphere, mesosphere, and thermosphere.

The troposphere consists of three-quarters of atmospheric mass, having a distance of around 8 to 14.5 kilometers.

Above the troposphere, lies the stratosphere, which is at a distance of 50 kilometers above the surface of Earth.

The mesosphere rises to 85 kilometers above the planet.

This one is at a distance of 600 kilometers from the surface of Earth.

3. Biosphere

The biosphere consists of all living beings, starting from animals, plants to single-celled organisms. It can also be said that the biosphere comprises biomes. Now, if you are wondering what is meant by biomes, here is the answer –

A biome is a community where animals and plants of the same nature dwell together, for example, desert and coral reef.

Animals and plants which dwell on land, precisely terrestrial life, have a zone ranging from 3 meters to 30 meters. Next, aquatic life exists around 200 meters below sea level.

However, an interesting fact is that some organisms can live beyond these distance ranges. For instance, few birds can fly at a distance above 7000 meters from the surface of Earth. Besides, microorganisms can survive far away from these levels as well.

Did You Know?

In the Marianas Trench, the Mariana snailfish is found to live below 6000 meters.

1. Lithosphere

The lithosphere, also referred to as the geosphere, encompasses Earth’s rocks. For instance, boulders of Mount Everest, Hawaii’s Mount Kilauea’s lava, Miami Beach’s sands, etc. are considered lithosphere components.

Moreover, this subsystem of Earth can be classified into 12 significant and some minor plates. They are as follows:

1. Eurasian

2. Indo-Australian

3. Philippine

4. Antarctic

5. Pacific

6. Cocos

7. Juan de Fuca

8. North American

9. Caribbean

10. South American

11. Scotia

12. African

These tectonic plates are in constant motion, and the result of friction between them leads to the formation of mountains, volcanoes, earthquakes, etc.

Next, let’s proceed with how all the spheres interact with each other.

How Do Earth’s Spheres Interact with Each Other?

All four spheres have their own identities, but they interact with one another. Scientific researches suggest that if there is an event in one subsystem, it affects the other ones as well. Many types of interactions are possible on Earth, and some of them are between any of the subsystems and the event.

In the above figure, you can see double-headed arrows that denote effects and causes of interactions that are applicable in both directions. For instance, a volcanic eruption has a direct and indirect impact on the atmosphere, hydrosphere, and biosphere.

Did You Know?

Mount Saint Helens in Washington erupted on the 18th of May, 1980, and had effects on the environment. This helped researchers to delve deep into the matter of the impact on the different subsystems of Earth.

Besides event and sphere interactions, several interactions occur among the spheres only. These take place in the form of chain reactions. Here is an example:

Volcano >> Lithosphere >> Atmosphere >> hydrosphere >> biosphere

You can see in the above image and reaction that a volcano is an event releasing a substantial amount of rough material. These materials (as nuclei) help in water droplet formation. After a volcano erupts, the number of rainfall increases. It helps in facilitating the growth of plants.

Apart from this interaction, some complex ones can also take place. Look at an example:

After a volcanic eruption, enormous amounts of sulfur dioxide are released, which mixes with water to produce sulfurous and sulphuric acids. These acids come down to Earth with rainfall and have adverse effects on the growth of plants. It also decreases the level of pH in water, affecting zooplankton and phytoplankton growth. Moreover, if photosynthesis occurs in less percentage, carbon dioxide concentrations will increase, resulting in global warming.

The above discussion must have cleared your concepts related to how Earth’s spheres interact with each other. For more such topics, download the app today and get access to online tutorials and study materials.

Studying the Four Spheres of Earth – Definition, Earth’s Subsystems and FAQs

You can start studying the Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs from ’s online learning platform. We make the learning process smooth and easy for all the students by providing you with a reliable study resource curated by subject matter experts in a simple language. Below are some tips you can follow while studying the Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs: 

• When you are reading or learning the concept of the four spheres of earth, you should note down all the important points and make a summarized version of the concept.  

• Go through all the explanations and definitions thoroughly to understand the importance of each sphere and how they affect each other. 

• Once you are done with the Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs, go through the questions given in your textbook exercises and try to answer them. It will help you test your knowledge and check whether you have understood everything about the earth’s subsystems or not. 

• Use different reference books and study materials available on to learn more about the four spheres of earth and enhance your knowledge. 

Importance of learning the Four Spheres of Earth – Definition, Earth’s Subsystems and FAQs

The Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs is one of the most important topics of Physics. Below are the reasons why you should learn this crucial concept: The Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs tells you about how the spheres of the earth interact with each other and affect the lives of all the living beings on the planet. 

• By learning the Four Spheres of Earth – Definition, Earth’s Subsystems, and FAQs, you can strengthen your knowledge of the Physics subject and score excellent marks in the final exam. 

• Once you have understood the concept of the four spheres of the earth, you will understand how human beings affect the subsystems and what you can do to improve the quality of these spheres.  

What is Friction – A Brief Outline

Friction can be defined as a force that creates resistance between the relative motions of two objects in contact. It mainly takes place due to microscopic irregularities which are present on the surface of both objects. It means that rougher the surface; the greater will be the friction between two objects and vice versa. 

Additionally, two main characteristics of friction are that it always takes place in the opposite direction of relative motion between two objects and parallel to the surface of contact. Besides, the use of friction in automobiles is one of its most essential functions in our daily lives.

How Does Friction Affect Cars?

Friction in the automobile aids it to move, turn corners or slow down when necessary. 

The various advantages and disadvantages of friction in automobiles have been listed below – 

• When a car or any other automobile starts, its tyres push against the road. As a reaction, the friction present between the car and road pushes back which acts as a forward motion that enables a car to move forward. 

• Friction in the automobile also comes in handy when a car is taking a turn at the corner of a road. As friction present between the road and tyres, wheels ‘grab’ on to the ground and stay put. It prevents a car from sliding while turning a corner, which is why a car can sometimes skid or slide on a muddy or wet road as they have less friction than regular roads. 

• Apart from movement, friction in a car or automobile slows down. Disc brakes of cars have a steel disc attached to wheels which can be found between the two small brake pads. When the brakes are pressed, brake pads push the discs on the car wheels which cause friction. This slowed down the wheels and finally stopped the car. 

• Apart from friction on cars, it also works the same in the case of bicycles. When the brakes on bicycles are applied, brake pads press down on bicycle wheel rims. It causes friction and slows it down.

However, friction in automobiles also generates heat which accelerates wear and tear of a car engine.  Furthermore, around one-third of a car’s fuel usage goes towards overcoming friction. 

Advantages and Disadvantages of Friction

In our day to day lives, friction is a necessary evil. For instance, without it, we wouldn’t be able to walk properly. Like friction in automobiles, when we walk, we push the ground with our foot, and as an opposite reaction, the ground too pushes us back. 

However, friction present between the road and sole of our shoe enables us to keep our grip and prevent slipping, which is why we tend to slip and fall on wet or well-polished surfaces.

Similarly, it is because of friction we can write and draw on surfaces like paper and blackboard. When we write, bits of lead and chalk break due to friction present between them and paper. These bits then cling to the surface and appear as writing or drawing. 

Types of Friction

To better understand friction and cars, one should have a detailed idea of four main types of friction – 

The frictional force that occurs between two objects when they are at rest is known as static friction. In this situation, acceleration can only take place when the force applied to the one object in rest can overcome the static friction. In other words, if there is no static friction, an object or body would continue to move. Examples of static friction include when a car is parked on a hill, a ball resting on the floor etc.

Sliding friction acts on an object or body when it is motion. It is also known as kinetic friction. The resistance offered by sliding friction is weaker than static friction. It is because a body in motion stays in motion, whereas it is more difficult to overcome the static force and move an object. 

The friction resisting movement of a rolling object or body is known as rolling friction. This type of friction has even lesser resistance than sliding and static friction which is one of the reasons it is easier to move a heavy object by rolling rather than by sliding. 

The friction faced by an object or body when it is moving through a fluid medium is known as fluid friction. Examples include resistance faced by swimmers when swimming, Skydiver falling towards the ground using a parachute etc.