How car insurance works?

How car insurance works?

Finding the proper automobile insurance is simpler than you think that

Especially if you are shopping online. In fact,

You can do coverage research,

Get a quote and buy your insurance from all of the comforts of your home. However,

Before you begin, you'll want to know the answers to this question:

1 What kind of car do you drive?
2 How many miles a year does one drive?
3. Where do you live?
4. What is your driving history?
5. Who will drive your car?

Your. Is there a gap in your car insurance coverage?

If you need to file a claim, you should contact your insurance company right now.

They will guide you through the filing process and get your car back on the road as soon as possible.

Does car insurance cover?

Your car insurance works by paying for physical injury and property damage claims filed against you after an accident.

This includes repairing damaged vehicles and treating you or your passengers.

Your policy may also cover any property damage from your accident

Some of the types of auto insurance coverage we offer include:

• Medical payment coverage
• No fault insurance coverage
• Conflict insurance
• Extensive car insurance
• Auto glass insurance coverage
• Auto towing coverage
• Rental car insurance coverage
• Liability insurance for physical injury
• Liability for auto property damage
• Uninsured motorist bodily injury
• Property damage to uninsured motorists

Do I need car insurance?

In most states you need to buy car insurance, getting adequate coverage is in your favor.
You should ensure the right amount of coverage to avoid providing the pocket for repairs or injuries.

Your car insurance costs will depend on a number of factors, including:

• Driving record
• Age and marital status
• Location of the house
• Car making and model

Without proper coverage you may also face fines and penalties.
For example, if a police officer finds out that you are driving without insurance, you can get a ticket or even suspend your license.

To avoid situations like this, get a car insurance quote and learn more about our great auto insurance coverage today.

Work: Power and Energy- inews71

In this chapter, we will see how a force works. In terms of physics, the word "work" has a definite meaning. We will see that a force working on something can move it and create kinetic energy. This kinetic energy can convert into potential energy and this transformation of energy is a very natural process and different types of energy can convert into one another. The most important aspect of science is energy and energy plays a most important role in the development of mankind so, how energy can be explored from nature will also be discussed.

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Work :
the term 'work' in various manners in our daily life. A gatekeeper guarding a house all day long, sitting on a tool, may claim to have done a lot of work, but in the words of physics, that is not any work. In terms of physics, the word 'work' is well defined. If a force F is applied on any object and the object traverses a distance s during the application of force (that is displacement occurs) then, the amount of work W done by the force is: 

W=Fs

Unit of work: J (Joule)  

Dimension of work [W] = ML2T-2

Force is a vector quantity and the distance traversed or displacement is also a vector quantity but in case of work the product of those two vectors is a scalar quantity. As individual vectors, there is no such condition that the direction of force and distance traveled has to be the same but in this book, we will only discuss the force and distance traveled in the same direction. 

Have you noticed, while discussing work, we said that the 'force' has done the work? A person or a machine may push any object to some distance by applying a force. In terms of daily life, we say that the person or the machine has done the work. But in physics, neither the person nor the machine does the work, always the force applied does the work. This force may be applied by a person or a machine. Let us assume that, you have pushed an object to a distance s by applying a force F and left it after setting it in motion. The object has traveled an additional distanced and at last, it has stopped. How much work is done? The amount of work done is W=Fs, as no force was applied while traversing the distanced, so no work is done.

Energy :
In our daily lives, we use the term energy for different purposes but in physics, it has a definite meaning. Generally speaking, there is no difference between applying energy or applying force, but in physics, these two phrases mean completely different things. In the previous chapter, we have learned what is meant by force, what is meant by energy will be discussed in this chapter. We all have a shallow idea about energy because we mention the words electrical energy, thermal energy when we make casual conversation. Sometimes we even hear about chemical energy or nuclear energy. Though light

It is not mentioned as energy, we can assume that light is one kind of energy too. The energy which is not mentioned in our daily conversation, but will be discussed a lot in physics is kinetic energy. We may think that there are many types of energy in nature, but it is interesting that all kinds of energy are the same and we can only transform them from one to another! So what is energy? The ability to do work is energy! Not only that, when a positive work is done by applying a force on an object, the force creates an energy in that object.

The amount of work done on the object is the amount of energy created in it, and the person who is applying the force has to give exactly the same amount of energy. So now you have understood the meaning of negative work. If any force does negative work on an object, then it is to be understood that a certain amount of energy is taken away from the energy contained in the object. The amount of negative work done is equal to the amount of energy taken away, and he who has applied the force gets this energy anyway. So, on any object 

Doing positive work -, giving energy to the object. Doing negative work —> taking away energy from the object. 

You can clearly understand that energy has no direction and it is a scalar quantity. As we produce energy by doing work or do work spending energy, these two have the same unit and the same dimension.

Sources of energy- inews71

Sources of energy :

The history of world civilization can be simply named as the history of utilization of energy. It can be generally said, how much a country is developed, a simple means to understand it is to calculate the use of electrical energy per person in that country. Different forms of energy in the world are shown in figure 4.03. 

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• Non-renewable Energy As the history of civilization on earth is actually the history of energy utilization, we see there is a hunger for energy in every country and every state in the world. Everyone is searching for energy and using it in every possible manner. Fuel Energy (Oil, gas, and coal): At this moment, the biggest sources of energy of the world are oil, gas or coal. Oil, gas or coal, are all fossil fuels that is, being buried under the ground from millions of years are transformed into this form due to a prolonged period of heat and pressure. Coal, oil or gas are to be extracted from beneath the ground.
• The oil that is extracted from the ground (Crude oil) is very dense at the primary stage, they are converted into petrol, diesel, or kerosene by refining in refineries and some other useful substances are found as well. The gas that comes out from beneath the ground is mainly methane CH4, water vapors and other gases can be mixed with it and these are to be separated. The gas of our country Bangladesh is comparatively much clearer 3. And suitable for direct use.

Nuclear Energy: Many countries are utilizing nuclear energy, and fuel is also required there, that fuel is uranium. There is a similarity in the energies, oil, gas, coal or uranium; they are spent when they are used. Men have already estimated the amount of uranium in the world or the amount of oil, gas or coal beneath the ground. It is seen that if people continue to use energy at the rate they are doing now, then the sources of energy like oil, gas, coal or uranium will run for two hundred years at best. After that our known sources of energy will run out. People are not that much concerned about what will happen then because they are almost sure that by them some other sources will be found using science and technology. For example, nuclear fusion, using which the sun or stars produce their energy. The fuel for fusion comes from one isotope of hydrogen and each molecule of water contains two atoms of hydrogen. So, there is no worry for that to run out. 

Renewable Energy: Human being is not only relying upon new forms of energy in the future but at this very moment, they are also dependent on the sources of energy, which will not be finished. This energy comes from sunlight, ebb, and flow of the waves of seas, winds in open fields, hot magma from the interior of the earth or currents of water of rivers. It is not difficult to understand that these sources of energy are almost inexhaustible. These are called renewable energy- i.e. the energy which can be renewed, and because of that, there is nothing to be worried about. At present one-fifth of the energy, people are using is this renewable energy. As days are going by, people are getting conscious about the environment. And so the use of this type of energy is increasing more and more. Hydroelectricity: One-fifth of the total energy of the world is renewable energy.

Most of that part is hydroelectricity, to produce electricity by making a dam in a river. Since the water of a river is inexhaustible, therefore the source of energy of such a power plant is inexhaustible. This is the conventional concept. But if a dam is built on a river, it harms the environment to a great extent; due to this, the people of the world have become very conscious. Those who are a little bit farsighted don't build such a power plant more. Biomass: After hydroelectricity, the most renewable energy comes from biomass, by biomass we mean wood fuel, straw, etc. People in many parts of the world have no oil, gas or electricity; they spend their daily life by burning fuelwood and straw. The used energy by these poor people is a major part of the total .0 energy of the world. Even the dried tree, straw, etc. are finished due to burning, biomass is called the source of renewable energy because the trees can be grown again. It is not lost forever from the world like oil, gas or coal.
The important sources of energy are solar energy, wind energy, biofuel and geothermal energy besides the two forms of renewable energy, hydroelectricity, and biomass. Solar energy: Many of you will be astonished on hearing, only in one square kilometer area we get one thousand megawatt energy from the sun as light and heat which is near to the energy of a nuclear power plant. One part of the light and heat that comes from the sun is absorbed by the atmosphere. It is absent at night and uncontrolled due to cloud and rain. Besides this, the energy comes as light and heat energy, it has to pass one step for conversion into electricity. It is still said to be the most reliable source of energy. Utilizing solar heat electricity can be generated. Nowadays a common picture of the earth is the solar panel, installing this on their roofs; people are generating their own electricity sitting in their own residence. 

Wind energy: After solar energy, wind energy has occupied an important place very quickly. In our country, we are not familiar with seeing large turbines for wind energy, but in many countries of Europe, this is a very familiar scene. The place at which the windmill is set up, a large tower is erected upwards, so there is no waste of land at all, for this reason, the environmentalists like it very much. From a wind turbine, it is possible to get a few megawatts of electricity! The utility of the energy that is generated by using air; is increasing by 30% every year. This number is not a small number at all. 

Biofuel: The people of the world are preparing alcohol for drinking purposes for a long time- it is one kind of fuel. Preparation of alcohol as fuels from food like popcorn and sugarcane is almost an acceptable procedure. The oil that we use for cooking purposes can also be used instead of diesel. There are many kinds of trees in the world from which we can get fuel oil directly. In many countries of the world, the research on biofuel is continuing, moreover many countries like Brazil have started using such types of biofuel on a large scale. 

Geothermal energy: Another important source of renewable energy is geothermal energy. The inner part of our earth is very hot, when a volcano eruption takes place then we become aware of it. So, if someone can make a hole a few kilometers deep, then he will get a giant source of heat energy. The process is still not easy so its large scale use has not yet started. In some places, due to its geographical nature, this type of energy is available easily and its use has started there.

Newton's Third Law. inews71

# Newton's Third Law 

We have learned from Newton's first law what happens when no force is applied. We have learned from Newton's second law what happens when a force is applied. We will learn from Newton's third law what type of reaction takes place between the two objects when an object applies force on another object.

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Newton's Third Law: When an object applies a force on another object, then that object also applies a force of equal magnitude on the first object but in the opposite direction. 

In physics, generally, Newton's third law is written as, "Every action has an equal and opposite reaction", although we have not written it in this form. By this time since we have a little idea about force, confusion may occur if force is termed as "action" or "reaction" "suddenly". Moreover, those who are the new learners of physics, their first question will be if every reaction (a force) has an opposite reaction (another force) then why action and reaction are not canceling each other, producing zero? For this reason, the third law will have to be written very precisely. The third law states that if there are two objects A and B, then when A exerts a force on B, then B also exerts a force on A. It is worth mentioning that two opposite forces act on different objects, never on a single object. If the two forces were applied to a single object, only then one could cancel the other. Here there is no scope of cancellation. 

The matter will be clarified with the help of some examples. Let us consider that a mass m is allowed to fall from a certain height (figure 3.12). We know that due to the earth's gravitational force, the mass m experiences a force F towards the center of the earth: 

F=GmMR2

Already we have seen that this force is written as mg. 

From Newton's third law we know that the mass m also attracts the giant earth towards itself. That force is also F but in the opposite direction. We do not bother about this force, the reason is that the acceleration of the earth due to this force can be determined: 

F=Ma

Here, M is the mass of the earth and a is the acceleration, 

Therefore, 

a=FM=mgM=mMg

If the mass of the earth is M= 5.98 x 1024 kg, then if an object of mass 1 kg is released from above then the acceleration of the earth will be, 

a = 1.6 x 10-24ms2

This is so small that nobody is bothered about it! Next time when you will jump anywhere, remember that you attracted the whole earth towards you when you were falling downwards. (As small as the acceleration of the earth may be, you pulled the whole earth towards you, you may be a little proud of it!) The easiest way of understanding Newton's third law is to understand the mechanism of our walking. We can all walk but nobody knows the physics hidden behind this.

Since you have started to learn physics a simple question can be put to you. Since you have walked from a stationary position, so you have an acceleration, that means force has been applied to you. But all of us know that nobody is applying a force on us. We walk by ourselves. How is that possible? Unless we know Newton's third law we never can explain the mechanism of walking. When we walk we exert a force on the ground (i.e. apply force). Then 

According to Newton's third law, the ground also applies an equal and opposite force on our body (Figure 3.13). This equal and opposite force creates the acceleration and we walk. The persons who have a little problem understanding this, they may be remind-end that it is easier walking on hard ground compared to the sandy ground. The reason is that it is not possible to apply force on the sand, sand is displaced. Therefore the reaction force in Newton's third law cannot be achieved properly.

The matter can be clarified more if one is allowed to walk on a very smooth surface lubricated with soap-water or oil! Their friction is hardly present so we cannot apply a backward force at all and due to this, we will not get any force on us as the reaction force. So we cannot walk at all (You may try if you don't believe it). If force is applied, equal and opposite force is found, but if we cannot apply force at all, how can we get a reaction force? Then how can we walk?

What is Motion? Information of Motion. inews71

There are many kinds of motion around us. When a person rides a cycle, it's a kind of motion. When a car moves, that is another kind of motion. When a plane flies, it is also motion. When the earth revolves around the sun, it is also a motion. When a hanging bulb oscillates, it is a kind of motion. When a bullet ejects from a rifle, it's a motion also. Apparently, it seems that all these several types of motion are of different types. But you will be surprised and happy to know that all these motions can be explained by a few number of quantities. In this chapter, those quantities, their units, dimensions and the relationship among them will be discussed.

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• Rest and Motion 

We don't have any problems in understanding which object is at rest or in motion around us. We observe by our eyes in such a way that when anything moves slightly, we can recognize it very quickly. So, we can realize very amazingly what the terms rest and motion mean. But in physics, it is not sufficient only to realize rather it has to be well defined. To define it, we can say briefly, when an object does not change its position with respect to time, then it is at rest. And when an object changes its position with time, then it is in motion. Now we need to explain the term 'position' properly. In our daily conversation, we use the word 'position' in different ways, but in physics, the word 'position' has a definite meaning. If you are asked, where is the position of your school and if your answer is 'Ailtuli', your answer is correct but the position of your school remains unknown. If you reply, your school is 1 kilometer far from the gate of your residence; the position of your school is still unknown. 

Though the position of the gate of your residence is known to us, yet we cannot tell exactly in which direction the school is situated at a distance of 1 kilometer from the gate. But if you say the school is situated 1 kilometer east from the gate of your residence, only then we will know the exact position of your school. That is to know the position of the school; we have to know both the distance and the direction definitely. Not only this, this distance and direction has to be specified from the position of a reference point. In the case of your school, the gate of your residence was the reference point of origin. Instead of your residence gate, the reference point might be a bus stop or a shopping mall. Then definitely both the position and the direction would have different values, but we can specify certainly the position with respect to the new reference point. That is, to specify the position of any object, it has to be mentioned with respect to a reference point. This reference point is not an absolute one; we can conveniently choose any point as a reference point or origin. 

Now the question is, to specify the position of an object, is it necessary for the reference point of origin to be a still point? Let us think, in front of you a person is sitting still on a chair. If we consider the chair as the reference point or origin, then we can firmly say, the position of your friend is not changing. 

If it happens that actually, you are sitting in a moving train, what will it then be?

A man outside of the train standing on the station will say, you and your friend are both in motion, nobody is at rest. Then whose statement is true? Your statement or of the man standing in the station. In fact, both are correct! The reason is- if the reference point or the origin moves at a uniform velocity, then we cannot tell firmly whether the reference point is moving at a uniform velocity or actually it is at rest and all other things are moving at uniform velocity in the opposite direction. Therefore we can say, if an object changes its position with respect to an origin, then the object is in motion with respect to that origin. It is not our headache whether the origin is at rest or moving at uniform velocity.

This is not important since every motion is relative. Not only this, if we want to search out an absolute rest reference point, we will be in trouble. If we consider anything on the surface of the earth as origin one can object, the earth is not stationary rather it is rotating about its own axis, so everything on its surface is also rotating. Alternatively, we can say, the center of the earth is the origin. Then someone else can come up with the objection that the center of the earth is not stationary, it revolves around the sun. Then we can say more intelligently, the center of the sun must be the origin! Then another person can confidently say that the sun is also not stationary it is also revolving around the center of our galaxy.

Surely you are feeling that no one can dare to say, the center of our galaxy is the origin! Who can say that the galaxy and the universe are stationary? Not only this, if the center of the galaxy is considered as the origin to describe any position on the surface, do you realize the extent of complexities that may arise? In fact, we don't need such types of complexities, for our purpose, we can consider any point as the origin, which seems stationary to us. In this case, we have to mention all the measurements are done with respect to this origin. In this way, scientists have done all the measurements starting from the nucleus of an atom to the satellites launched in space, with no problems what so ever!

Inertia and Concept of Force- Newton's First law. inews71

∎ Inertia and Concept of Force- Newton's First law 

In the previous chapter, we have learned about velocity, speed, acceleration (and deceleration), elapsed distance and their mutual relationships. We have deduced the equations of motion and applied them to solve problems related to motion as well. In this chapter, we will learn how motion can be created or motion can be influenced by applying force. 

Newton's First law of motion: Newton's first law of motion can be expressed as-A A stationary object will remain stationary and an object in uniform motion will continue its uniform motion unless a force is applied to it. (Since velocity is a vector quantity, for uniform motion the object will not change its direction of motion; it will move along a straight line at uniform speed.) 

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The first part of Newton's first law is not difficult to understand because we always observe that the bodies at rest remain at rest and do not move until pushed. The problem arises from the second part because we never observe that a body in motion keeps its perpetual motion forever. If motion is produced in a body by pushing it, we observe that the body comes to rest if no force is applied. From our daily life experiences, it seems that to keep a body in uniform motion we have to apply force on it continuously. Form Newton's first law we learned that it is not true. If a body in uniform velocity stops then we have to realize that force has been applied by some means. Friction, air resistance, etc. actually stop a moving body by applying force in the opposite direction. If all these forces could be withdrawn, then we would find that a body in uniform motion keeps its perpetual motion forever.

∎  Inertia 

The characteristic that a stationary body wants to be stationary or a body in motion wants to keep its motion, unless a force is applied, is called inertia. When a car at rest suddenly starts moving we move backward, this is an example of inertia. The lower part of the body is attached to the car. When the car starts moving, the lower part of the body moves with the car but the upper part of the --,°° body is still stationary and tends to remain stationary. So the upper part of the body moves backward. Since this inertia is due to the tendency of rest, this is called inertia of rest. 

When people get down from moving bus, train, etc. we see they fall down due to the inertia of motion. The whole body of the person on a moving train or bus is in motion. When his or her leg touches the ground, the lower part of his/her body comes to rest, the upper part of the body keeps moving forward due to the inertia of motion. So the person falls down.  

If the term 'inertia' was merely a definition then it should not be taught with so much importance. Actually from the viewpoint of physics, it is a very important topic. Up till now, we have not uttered the word mass, but to know the motion of an object we have to know its mass. We do not treat a light cycle and a heavy truck coming with the same speed on the same scale. The reason is the difference in mass. But actually what is meant by mass? Often we say 'mass' is a measure of the amount of object. But a more scientific answer is 'mass' is the measure of inertia.

(Consider the matter seriously- a very important statement has been made). If a body has a higher inertia, then you have to understand that surely it has a higher mass. If inertia is less, then the mass is also less. You definitely observed that the object with higher mass cannot be displaced by a higher amount by the application of an equal amount of force. But a body with less mass can be displaced easily. Or otherwise, we can say, if the mass is less the influence of inertia is reduced comparatively. 

∎ Force 

The word "force" is used for the first time in Newton's first law. But the interesting thing is, what do we mean by the word 'force' is still not described. If it was another book other than physics then instead of using the word `application of force' if we use the word 'application of energy' then the meaning of the sentence will not be changed significantly. Since it is a book of physics, hence we cannot use the word 'energy' here. In physics, the word `energy' is a completely different quantity. Here we have to actually use the term `force'. But what is meant by force? Still, now we have not given the definition of force. Actually, Newton's first law of motion can be the definition of force. Force is that quantity the application of which a stationary object start move and a body moving, with a uniform velocity change its velocity.

From Newton's first law we can understand, what force is but cannot measure it. But from the second law, we will learn to measure force. When you use force in your daily life for different purposes, you may realize that for the application of some forces it is necessary to come in contact with the object (e.g. to lift heavy objects with the help of a crane, to push anything or coming to rest of moving objects due to friction). Whereas you may have noticed that for the application of some other forces, it is not necessary to come into contact with the object (falling of anything downwards due to gravitational force, attraction by magnets). So we can divide forces into two types, contact forces and non-contact forces.

But you definitely understood that the region we assumed to touch, but at that region, the molecules, atoms and their revolving electrons of each other do not create force by direct touch rather one is working with the other by their electromagnetic forces. In other words, we can say, if we go to the atomic scale, then all the forces are non-contact in nature. One atom attracts or repulses another atom at a distance; they need not touch practically.

Different Types of Motion. inews71

• Different Types of Motion 

We see various types of motions around us, vibrations, rotations, and separations — all these are examples of different kinds of motions. Probable motions are unlimited, but if we wish, we can talk about some important types of motion separately. Linear motion is an example of the easiest type of motion. If anything moves along a straight line then its motion is a called linear motion. If an object is pushed off on a plane surface then it moves along a straight line. If a ball is allowed to fall from a height, it will fall straight downwards, so it is also a linear motion. 

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• 
  Circular Motion 

When a body rotates a few particular points or a line, keeping the space of the particles of the body unchanged, it's called circular motion. Though the motion of electric fans, hands of clocks, etc are the examples of circular motion, a wonderful example of circular motion is the moon in the sky. Moon is not tied by to the earth although it is revolving around the earth, neither is it falling on to the earth's surface. 

• Translational motion 

If an object moves in such a way that all the particles of the object travel the same distance, at the same time, in the same direction then its motion is called translational motion. Sometimes we see many examples of this type in our surroundings. When something moves in a straight path then its example is very common. If we do not consider the circular motion of the wheel of a car then straight advancement of the car is an example of translational motion. At this time every point of the car will travel the same distance, in equal time, in the same direction. 

There is no obligation that the translational motion will be straight. But the example of translational motion is not easily available in the case of a curved path. Figure 2.01 shows how a plane has to move for every point of the plane traveling equal distances in the same direction. The figure also shows why the example of translational motion on a curved path is so rare. 

• Periodic Motion 

If the motion of a moving object is such that it passes repeatedly through a definite point in the same direction in the same manner in a definite interval of time, then this motion is named a periodic motion. The vibrational motion of our heart is periodic since it vibrates in the same direction in the same manner after a definite interval of time. The periodic motion may be circular (motion of the blades of a fan), hyperbolic (orbit of Haley's Comet around the sun) or linear (oscillatory motion of an object hanging from a spring). Circular motion is a special type of periodic motion. 

• Simple Harmonic Motion 

Simple periodic motion may be a special sort of periodic motion. In the case of oscillatory motion, the object oscillates on both sides of a definite point. Starting from its complete rest position, the objects start moving slowly. When the object comes to the center it has the maximum velocity, then its velocity starts to decrease until it comes to rest. Then it changes its path of motion and moves in the opposite direction. In the opposite direction when maximum velocity is attained, then its velocity decreases again. It stops its motion completely and starts to repeat its motion slowly again in the previous direction.
It continues its motion in this fashion. There are so many examples of oscillatory motion around us. The motion of an object hanging from a spring is an example of an oscillatory motion. The oscillatory baby on a swing (Figure 2.02) or the pendulum of a clock are the examples of oscillatory motion. When we speak then the air molecules carry the sound forward by this type of motion. So far we have discussed some special types of motion but the causes of these motions have not been mentioned anywhere. The major success of physics is that not only can it find the causes of the different types of motion of objects but it can also explain the motion very clearly. Can you guess the cause of the motion?

Effect of Force on Motion: Newton's Second Law- inews71

In the football ground, we always see that a player kicks a stationary football and directs it to distant places creating motion. At the time of the kick, when the player touches the ball, only at that instant, force is applied on the ball. The stationary ball goes into motion due to this force. We can apply force also for a long time instead of just for a moment. By pushing a stationary go-cart for a long time and we can release it after setting it into motion. It can move for a while until it ceases its motion due to friction. The direction of velocity can also be changed by the application of force. When a bowler throws a cricket ball towards the batsman, then the batsman can direct the ball totally in a different direction by hitting the ball with his bat. In the three examples described above, we see that velocity is changed by the application of force on an object for a short or a long time. In the previous chapter, we have seen that the rate of change of velocity is acceleration. Therefore we can say when force is applied on an object, acceleration is produced. The relation between the force applied on a body and the acceleration is Newton's second law. 

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Newton's second law: The rate of change of momentum of a body is proportional to the applied force acting on it and the change of momentum also takes place in the direction in which the force acts. 

If a body is moving with an initial velocity u and the velocity is changed (by increasing or decreasing) from u to v after a time t. 

Therefore, change of momentum: 

mv-mu

So, the rate of change of momentum: 

mv-mut=m(v-u)t=ma

Since we considered that there is no change of mass, so we can write like this. Further, we know that acceleration is: 

a=(v-u)t

Therefore if the applied force is F, then we can write Newton's second law of motion as: 

            F or ma 

But we don't want to express the law in proportional form, rather we want to write it as an equation. 

Then using a proportionality constant k, we can write 

F = km

In the case of Newton's second law, it is possible to create an amazing result. Since the term 'force' is not explained anywhere, (Newton's first law gives the concept only) by using the second law this will be measured for the first time. So, we have to give a value for the constant. We can say, when Newton's second law will be applied, if the proportionality constant is considered as 1, then the equation we will get is the measure of force. How easily a proportionality relation is converted into an equation. Therefore, we can write Newton's second law of motion as an equation. If the force is F and the proportionality constant is considered as 1, then 

F - ma 

That this small and simple equation can make a revolutionary change in the world of physics is difficult to believe. 

The unit of force is Newton (N). Dimension of force is [F] = MLT-2 

It has to be remembered that Newton's second law of motion is true not only for linear motion but this is true for any type of motion. We have known about gravitational force, by using Newton's second law, we will be able to explain the motion of the planets revolving around the sun due to the gravitational force. But in this book, we will limit the use of Newton's second law only to linear motion. If force is applied to an object, then by using Newton's second law, its acceleration can easily be determined. (If force is divided by mass, acceleration can be found). If acceleration is known, the velocity or distance traveled can be determined by using the laws of motion. 

Otherwise, we can say that if we see an object in motion and can calculate its acceleration, then if its mass is known, it is possible to calculate the force acting on it.

Nature of Fundamental Forces. inews71

#Nature of Fundamental Forces 

If you are asked how many types of forces are there on the earth? You certainly will say, many types. If we push anything this is a force, when a truck carries or pulls a load this is a force, when a tree is uprooted due to a storm this is a force, when a magnet attracts iron this is a force when houses are blown away in bomb blasts, it is a type of force, it is a force, when a crane lifts something this is force. If you are given some time, you can prepare a big list of such types of forces.

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But do you know the amazing matter? There are only four types of forces in nature, if the forces described above are analyzed, you will find that they are not outside these four types. Fundamental forces are actually only four in number. These are; gravitational force, electromagnetic force, weak nuclear force and strong nuclear force. 

• Gravitational Force 

All objects in the universe attract one another by a force due to their mass. This force is called the gravitational force. Due to this gravitational force, the stars are revolving around the galaxy or the earth is revolving around the sun and the moon is revolving around the earth. When the force of gravitation of the earthworks on us, we call it gravity. This gravity pulls us towards the center of the earth i.e. pulls downwards and due to this pull, we feel our weight. Force of gravitation is an amazing force of physics. An object that has mass attracts another object by the gravitational force. In this chapter, we shall discuss the gravitational force a little bit more in detail. 

• Electromagnetic Force 

We have seen, now and then, that when we comb our hair with a comb it attracts pieces of papers. We have also seen that a magnet attracts or repulses another magnet. Though we think that electric and magnetic forces are different in nature, actually the two forces are identical. They only appear in two forms. Only and this electromagnetic force can attract and repulse but the other forces can attract only, cannot repulse. It is so much stronger than gravitational force (1036 times, or trillion times stronger). That the statement is true, you can definitely guess. Because when you comb your hair by a comb and pull a piece of paper by attraction, then the whole earth tries to pull the piece of paper by the gravitational force due to its total mass. But the small amount of electricity in your comb defeats the total gravitational pull of the giant earth. 

• Weak Nuclear Force or Weak Force 

It is called weak because it is weaker than the electromagnetic force (approximately trillion times weaker) but not at all weak like the gravitational force. The force of gravitation and the electromagnetic force can act from any distance but this force acts for a very small distance (10-18 m). The emission of beta

• Strong Nuclear Force 

This is the strongest force of the universe; this is a hundred times stronger than the electromagnetic force but it too acts at a very small distance (10-'5 m). We know the nucleus is situated at the center of the atom and the strong force acting between the protons and the neutrons within the nucleus confines them. Confined due to this strong nuclear force, the nucleus contains an enormous amount of energy. Therefore by the division of a large nucleus or by the addition of small nucleuses a huge amount of energy can be produced due to this force. For this reason, a nuclear bomb has so much energy. By this force light and heat are produced in the sun.

The scientists think these four types of forces have the same origin and they are trying to explain all these forces by a single law. Meanwhile, it has become possible to explain the electromagnetic force and the weak nuclear force by a single law. This is a tremendous success in theoretical physics. (Therefore, you can say, forces are of three types: gravitation, electro-weak, and nuclear force. Nobody will say it is wrong). The scientists are trying to unify the other forces too by a single law.