Category: Physics Notes PPT

Chapter 10 class 11 in physics is the mechanical properties of fluids. Students get to score higher scores in subjects like physics because the questions in competitive exams from the subject are based on basic concepts, formulas and problems related to the chapter. Theories are difficult to memorize and hence, there arises a chance of losing marks. In this chapter, our experts have tried to explain these concepts in detail so that students find it easy to understand and practice problems on the basis of understanding of the chapter.

In this chapter, students may learn in detail the mechanical properties of liquids and gases, pressure, streamline flow, viscosity, surface tension and so on.

Introduction

As we all know, a fluid is anything that has no fixed shape. Both liquids and gases are referred to as fluids because they have the tendency to flow. Fluids can yield to slightest external pressures. The study of mechanical properties of fluids is called Hydrostatics. The volume of liquid or gas depends on the pressure acting on it. Since liquids have a fixed volume, the change in volume due to the change in external pressure is less. It is not the same in the case of gases, as they do not have a fixed volume.

Let’s study more about the concepts of mechanical properties of fluids

Notes of Mechanical Properties of Fluids

Fluids are liquids and gases with the property to flow in a certain direction on the application of external force. Two major topics are studied when we talk about the mechanical properties of fluids. They are- hydrodynamics and hydrostatics.

Hydrodynamics

In physics, hydrodynamics is the study that concerns the forces acting on or exerted by fluids. It deals with the motion of fluids and the forces acting on solid bodies that are immersed in fluids. It also focuses on the motion relative to them. In short, it is the study of fluids in motion. Thus, it is a vast branch of science, which we will study more later.

In this chapter, we will focus more on Hydrostatics

Hydrostatics

This branch of physics is concerned with the fluids at rest.

Pascal’s Law

Pascal made an observation that the pressure in a fluid that is at rest is the same at all points, provided they are at the same height. He also inferred that the pressure difference depends upon the vertical distance between the two points. Thus, the pressure difference applied to the fluid which is enclosed can be transmitted undiminished to every point of the fluid and the container vessel’s walls as well.

It can thus be noted that when an incompressible fluid is passing between every second in a pipe of non-uniform cross-section, the volume will be the same as the steady flow.

Bernoulli’s Principle and Equation

Bernoulli’s principle states that the total energy of the water always remains constant, therefore when the flow of water in a system increases, the pressure necessarily decreases. When water starts to flow in a hydraulic system the pressure drops and when the flow of water stops, the pressure rises again.

Therefore, in a hydraulic system, the total energy head is equal to the sum of three individual energy heads.

This can be expressed as follows-

Total Head = [Elevation Head + Pressure Head + Velocity Head]

Where,

• Elevation head- is the pressure due to the elevation of the water

• Pressure head- is the height of a column of water that a given hydrostatic pressure in a system could support

• Velocity head- is the energy present due to the velocity of the water.

Surface Tension 

The amount of energy required to increase the surface of the liquid by unit area is defined as surface tension. It means it is the property of the surface of the liquid to resist force. Moreover, it is the force that holds the liquid molecules bound together. Therefore, surface tension is the amount of the extra energy which the molecules at the interface have when compared to the interior. Surface tension is denoted by the Greek letter ‘sigma’.

Viscosity

Viscosity is the measure of the resistance exerted by fluids to gradual deformation by shear or tensile stress. Thus, it can be considered as the fluid’s resistance to flow. When we say honey is thicker, milk is thinner, we intend to mean the viscosity of the liquid. Thus, the liquid that tends to flow less is more viscous.

It is measured in terms of a ratio of shearing stress to the velocity gradient in a fluid.

The equation to determine the viscosity of a fluid

When a sphere of radius a is dropped in a fluid of viscosity v, the viscosity is given by η=2ga2(Δρ)9v

Where,

• ∆ρ is the density difference between the fluid and the sphere

• a is the radius of the sphere

• g is the acceleration due to gravity

• v is the velocity of the sphere

Minute is one of the most generally used units of time. Formerly, it was well-defined as the 60th part of an hour. The average period of earth rotation relative to the sun, which means the 1440th part of the mean solar day also, defines the min. 60 seconds make one min, and 60 minutes make an hour. It means that different times, minutes, seconds, and hours are related to each other.

Moreover, it’s straightforward to convert second into minutes or vice-versa. Similar to it, one can convert minutes into an hour and vice-versa in simple steps. The minute meaning and the relation of min with other units of time are discussed below.

Definition of Minute

Mins refer to a sixtieth of angular measurement degree. It refers to a period, which is equal to one-sixtieth of an hour and sixty seconds. 

Process of Converting Seconds to Minutes

In one min, there are 60 seconds. The process of converting number given in seconds into minutes is as follows:

• Label the given number of seconds as sec and multiply the number by 1/ 60. This fraction shows that there are 60 seconds in a minute. After multiplying, the correct unit in a minute can be obtained. It is the same way as dividing the given number by 60 seconds. For example, if there are 3600 seconds, then by dividing it by 60 seconds, the answer will be 60 minutes. Mathematically,

3600 sec/ 60 sec = 60 min

The above picture shows the conversion of a second into minutes and back minutes into seconds.

• If the decimal is obtained by dividing the given number by 60 seconds, then convert it back into sec by multiplying with 60. This decimal denotes the number of seconds left. For example, converting 7600 seconds in minutes gives:

7600/ 60 = 126.6 min

Now, 0.6 x 60 = 36 seconds

Hence, the final answer is 126 minutes and 36 seconds.

Process of Converting Minutes to Hours

In one hour, there are 60 minutes. The process of converting the number given in minutes into the hour is as follows:

• Label the given number of minutes as mins and multiply the number by 1 hr/ 60 min. This fraction shows that there are 60 minutes in an hour. After multiplying, the correct unit can be obtained. It is the same way as dividing the given number by 60 minutes. For example, if there are 120 minutes, then by dividing it by 60 minutes, the answer will be 2 hours. Mathematically, it can be represented as:

120 mins x 1 hr/60 min = 2 hr

Multiply the given number in an hour by 60 minutes to get the final answer in minutes. For example, multiplying 3 hours by 60 minutes gives 180 minutes. Mathematically, 

3 hrs x 60 min = 180 min

• However, if the given number is in hours and minutes like y hours z minutes, then a different procedure is followed to convert it in minutes. One has to convert y hours into minutes by multiplying it by 60. After that, add the obtained number in minutes to the z minutes given. For example,

Convert 2 hours and 45 minutes to minutes.

To do these, convert the given 2 hours into minutes by multiplying as 2 x 60 = 120 minutes. 

Now add 120 minutes to 45 minutes, i.e., 120 + 45 = 165 minutes. 

Minutes in Quarter of an Hour

One hour equals 60 minutes. One-quarter of an hour is written as ¼. 

For finding a total number of minutes in a quarter of an hour, multiply ¼ with 60 minutes. It gives:

(¼) x 60 min = 15 min

• Continuing this way, one can calculate the total number of minutes in two-quarters of an hour, three-quarters of an hour, and so on.

Conclusion

Minute is a vital time unite and possesses relation with different units of time. By going through with the above conversion ways, one can understand how to change the minute unit into an hour and second.

Distance

• Distance is the total path covered by the object in the given interval of time.

• Displacement is the shortest path covered by the moving object within the given interval of your time .

• Distance=Speed×Time.

• Unit of distance is usually measured in units of length like metres, kilometres etc.

Introduction to Motion

• An object is claimed to be in motion if it changes its position with reference to time. Eg: A car moving on a road.

• An object is claimed to be at rest if the thing doesn’t change its position with time. Eg: A person standing on the ground.

Basics of Standard Units

Units and their Standardization

• The standard unit of distance is in metres.

• The standard unit of your time is in seconds (s).

• The standard unit of speed can be measured in metre per second (m/s).

Basics of Motion and Its Types

Types of Motion

Types of motion are generally divided into parts – 

1. Rectilinear / Translatory motion: When a body occupies a line , without changing its direction, then the body is claimed to possess translatory/rectilinear motion. Eg: A car moving on a straight road.

2. Circular Motion: When a body moves within the shape of a circle with a few fixed points and a hard and fast radius, then the body is claimed to be in circular motion. Eg: Motion of planets around the sun.

3. Period / Oscillatory Motion: When the motion of a body repeats after fixed intervals of your time , then the body is claimed to within the periodic/oscillatory motion. Eg: The movement/motion of a pendulum that is to and fro. 

Periodic or Oscillatory Motion

• Periodic or oscillatory motion is that the motion during which a body repeats its motion after fixed intervals of your time .

• Eg: The movement/motion of a pendulum that is to and fro, Motion of a car in a circular path, Motion of planets around the sun.

Oscillations of a Simple Pendulum

• When the bob of an easy pendulum moves from its mean position B to A and back to B again, then from B to C and back to B again, the pendulum is said to complete 1 oscillation.

• In the case of the simple pendulum, the time period is the total time taken by the pendulum to complete one oscillation.

Time and Speed

Speed (Average Speed)

• Speed is the total distance travelled by the object in a given interval of time.

• Speed = Distance travelled/time taken

• Unit of speed is generally measured in metre per second(m/s), kilometre per hour(km/h).

Uniform and Non-Uniform Motion

1. Uniform Motion: When an object moving along a line moves with a continuing speed, then the thing is claimed to be in uniform motion. Eg: A car moving in a straight line with a constant speed.

2. Non-uniform Motion: When an object moving along a line changes its speed with reference to time, then the thing is claimed to be in uniform motion. Eg: The motion of a train.

Measurement of Time

Unit of your time is usually measured in seconds, minutes, hours. The time period is the total time taken by an object to complete one oscillation.

Units of Time

Unit of your time is usually measured in seconds, minutes, hours.

Units of Speed

Speedometer and Odometer

Visualizing Motion

Distance-Time Graph

Nowadays, information, messages, data, and signals are sent from one location to another within seconds. How is such fast transmission possible? The communication system uses modulation to enhance the range of the signals. Most of the signals generated in daily life are sinusoidal waveforms. Sinusoidal wave is a curve that describes smooth repetitive oscillations. The signals transferred during communication include crucial information in the form of a sinusoidal wave. Modulation and its types play a crucial role in the rapid transmission of the signals from the sender to the receiver. Modulation is the superimposition of the signal wave (carrying the message) with a high-frequency carrier signal to ensure faster transmission of the signal. 

What is Modulation And Its Types?

Modulation is one of the crucial branches of electronics science that is widely used in communication systems. It includes the different fundamental properties of the signal to transpose it from one location to another. 

Types of Signals used in the Modulation

• Modulating Signal: This is the signal that contains the message to be transmitted from the sender to the receiver and is called a message signal. Generally, the message signals are the band of low or high frequencies and are often called baseband signals. The message signals are the signals to be transmitted from the sender to the receiver. The frequency of the message signals to be sent is generally low. Thus, these signals undergo modulation to get correctly transmitted from one location to another.

• Carrier Signal: The other signal used in the process of modulation is the carrier signal that has high-frequency sinusoidal waves. The high-frequency carrier wave can travel much quicker as compared to the baseband signal. These signals have a specific frequency, amplitude, and phase, but no information. After modulation, carrier signals are used to transmit the signal to the receiver. 

• Modulated Signal: After the modulation is done, the resultant signal refers to the modulated signal. This signal is the mixture of the carrier signal and message signal. 

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The diagram shows three types of signals, namely, message signal, carrier signal, and modulated signal that is the mixture of the message and carrier signal.

What Are The Types Of Modulation?

There are generally three types of modulation:

• Amplitude Modulation: By superimposing the base signal with the carrier signal having a different amplitude, but the same frequency, if the amplitude of the base signal modifies or modulates, then it is said to be amplitude modulation.

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The diagram shows the amplified modulated wave after superimposing the message signal with the carrier signal.

• Phase Modulation: It is the type of modulation in which the phase of the base signal changes while superimposing it with a carrier signal. 

• Frequency Modulation: By superimposing the base signal with the carrier signal having a different frequency, but the same amplitude, if the frequency of the base signal modifies or modulates, then it is said to be frequency modulation.

What is the Need for Modulation?

The baseband signals transmitted by the sender are not capable of direct transmission. The strength of the message signal should be increased so that it can travel longer distances. This is where modulation is essential. The most vital need of modulation is to enhance the strength of the signal without affecting the parameters of the carrier signal.

Modulation has removed the necessity for using wires in the communication systems. It is because modulation is widely used in transmitting signals from one location to another with faster speed. Thus, the modulation technique has helped in enhancing wireless communication systems.

Modulation and its types prevent the interference of the message signal from other signals. It is because a person sending a message signal through the phone cannot tell such signals apart. As a result, they will interfere with each other. However, by using carrier signals having a high frequency, the mixing of the signals can be prevented. Thus, modulation ensures that the signals received by the receiver are entirely perfect.

The signals within 20 Hz to 20 kHz frequency range can travel only a few distances. To send the message signal, the length of the antenna should be a quarter wavelength of the used frequency. Thus, modulation is required to increase the frequency of the message signal and to enhance its strength to reach the receiver.

Length of the antenna can be easily calculated using this formula: 

L = λ = u/ν

= (3 x 108) / ν

Here, L = length of antenna 

        λ =  wavelength of the transmitted signal

        ν = carrier wave frequency

What are the Uses of Modulation?

• One of the most common uses of different types of modulation is the inter-conversion of signals from its existing to another form. 

• Digital Modulation is used for the transmissions of the digital signals over analog baseband. 

• Analog Modulation is used to transfer the low bandwidth signals such as TV or radio signals over a higher bandwidth. 

• Modern modulation techniques are widely used to carry out FDM, that is, Frequency Division Multiplexing

Non-contact force is a type of force that acts on the object, without any physical contact with it, the most familiar type of non-contact force is gravity which confers with the weight. In comparison to the contact forces, only there are a few non-contact forces. Some of the examples of non-contact forces are:

This page will help us understand the types of non-contact forces with examples.

Examples of Non-Contact Forces – Explanation

Gravitational Force

This type of force is responsible for bringing the items that are tossed back to the air. When any object is at rest on the surface, it exerts a downward force that is equal to its weight and this downward force is known as the gravitational force.

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Gravitational force is a type of attractive force that exists between all bodies having the mass, gravitational force of the sun keeps the sun and all the other planets of the solar system in a fixed orbit. Gravitation force is not required to be contacted to excerpt its downward force.

There are many advantages of non-contact gravitational force, it is a kind of constant force that keeps things in place. Gravity keeps our muscles and bones up and working, and it allows the earth to retain its atmosphere. And gravity is able to store some energy as potential energy, it allows it to harness, its example is a water dam.

Electrostatic Force

This force is very similar to the gravitational force, the main difference here is gravitational force acts between masses, and an electrostatic force acts between the two charged bodies.

This force can be generated by rubbing the comb on your clothes and then holding it near tiny pieces of paper, you can observe bits of paper standing on their end attracted to the comb. Everything is made of tiny positive, negative and neutral particles, the opposite charges attract each other and the like charges repel, this is the result of the electrostatic forces.

Magnetic Force

Consider, if you push the ends of the magnet together the second magnet will bounce off, this is the result of the magnetic force. It is also responsible for the attraction of iron by the force of magnets.  The magnetic force of the magnet goes on decreasing with an increase in the distance of the magnets.

The different sorts of attraction in magnetism are as follows:

1. Diamagnetism

2. Ferromagnetism

3. Paramagnetism

4. Antiferromagnetism

5. Electromagnetism

Nuclear Force – Strong and Weak Force

The nuclear force is one of the strongest forces in nature. The nuclear forces are further subdivided into weak nuclear force and strong nuclear force. Let us understand these in detail. 

Strong Nuclear Force

It is a short-distance force, which takes place between the fundamental particles within the nucleus. A strong nuclear force is charge independent and acts equally between a proton and a proton, and a neutron and a neutron, and a proton and a neutron, the strong nuclear force is the strongest force in nature. Because its range is small, strong nuclear force mediates both nuclear fission and fusion reactions.

Weak Nuclear Force

This force mediates the beta decay of a neutron, in which the neutron decays into a proton. And in this process, it emits a beta particle and an uncharged particle called the neutrino. It plays an important key role in the supernova, both the strong and weak forces form an important part of quantum mechanics.

Examples of Non-contact Forces

Various Non-Contact Force examples from our daily life are provided below.

1. An apple falling down from a tree is one of the best examples of the gravitational force, which was observed by Newton.

2. Iron pins get attracted to the magnet bar without any physical contact, due to the magnetic force.

3. The falling of raindrops on earth is also an example of non-contact force, which acts due to the gravitational force.

4. The charging of the hair and attraction of paper bits towards it you would have observed generally is due to the electrostatics.

5. When two magnets are placed close to each other is also an example of non-contact forces.

6. The ball falling freely in the virtue of gravity towards the earth is due to the gravitational force.

7. Even leaves falling from the tree is an example of a non-contact force.

8. Electromagnetism is another example of a non-contact force.

9. You can see various examples of electrostatics, which shows the attraction of small material towards an object.

10. When an electric current is passed through iron converting it into an electromagnet, it attracts iron and particles towards it, thus, displaying non-contact force properties.

Difference Between Contact and Non-Contact Forces

An optical instrument is a device that processes light waves, either to enhance an image for just viewing purposes or to analyse and determine its whole characteristic properties. Commonly used examples of optical instruments include periscopes, microscopes, telescopes, and cameras. Optics is also one of the branches of physics that observe and study the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. The term optics usually describes the common behaviour of visible, ultraviolet, and infrared light.

Optical systems often use transparent materials like glass or plastics with a refractive index selected to bend the light rays to form any type of desired images. And in the case of the human visual system, our eyes have to form images of a large field of view for objects placed at different distances with high resolution at least at a central area of the retina and the most important thing is that these tasks have to be accomplished using living tissues present in the human system. Naturally, the eye as an optical instrument is really very important because our vision is only good when the images formed on the retina are found and formed as high-quality images. If the retinal images are too blurred, the visual system will not work properly and we cannot view the objects clearly.

Optical instruments are the devices that process light waves to enhance the look of an image for a clear view. Besides magnifying distant or tiny images, these devices are used to analyse the properties of optical materials and light. Using an optical instrument (simple magnifying glass, or complicated telescope or microscope) you can make the object look bigger to see fine details on them easily. Remember that for obtaining a bigger image of any object, you have to use converging lenses or mirrors. It is because diverging lenses or mirrors always produce images that are virtual, upright, and smaller than the objects. It means that if you want to understand the concept behind the working of optical instruments, you should know about converging and diverging lenses. So, let’s start. 

When using a converging lens, it is crucial to remember some rules like if the object is far, then the image will be small and close to the focal length. As the object moves towards the lens, the image enlarges and moves beyond the focal length. If the object is placed at 2F, which is twice the focal distance from the lens, both the image and object become the same in size. When the object moves towards the focal point (F) from 2F, the image keeps moving away from the lens and growing until it reaches infinity (∞) when the object reaches F. If the object moves (more) closer to the lens, the image moves towards the lens from negative infinity and becomes smaller. The closer the object gets to the lens, the smaller the image becomes. Note that the converging mirror also works on the same rules.

Now, if we talk about a diverging lens, it is defined as a lens that causes a beam of parallel rays falling on it to diverge after refraction. Because of being thinner at the centre in comparison to the edges, a diverging lens always produces a virtual image. Unlike any converging lens, the diverging lenses always produce images that are located on the same side of the lens where the objects lie, virtual, upright, and reduced in size, i.e., smaller than the specified object. Besides, as the location of the object does not affect the image, the characteristics of the images formed by diverging lenses are easily predictable.

Thanks to our scientists and inventors with the help of whom, we nowadays, are available with a wide range of optical instruments. Being one of the most useful devices of optical science, instruments like a telescope, microscope, and many others play a vital role in our lives. These are used in performing various tasks and thereby have their applications in several areas. 

Applications of Optical Instruments

Multiple Lenses: As the word multiple suggests, these are devices that include multiple lenses. There are several devices like microscopes and telescopes that use multiple lenses to form images. By analysing any system with multiple lenses, we can conclude that it works in stages where each lens creates an image of the object. As per the working procedure, the original object in such devices acts as the object only for the first lens, and the object for the second lens will be the new image formed by the first lens and so on.

To understand this, you can go through the below examples.

1. Microscope

A microscope is one of the most widely used optical instruments consisting of only one lens or combination of the lenses for magnifying and inspecting bodies which are too small to be seen in detail by naked eyes. Earlier microscopes had only one lens, and therefore, known as simple microscopes, but the present microscopes are available with at least two lenses and thereby, termed as compound microscopes. 

In general, a microscope consists of two converging lenses. The main reason for including two lenses instead of one is that with two lenses, it is easier to get remarkably higher magnification. For instance, if you want a magnification of 35, you can use the first lens to magnify by a factor of 5 times and the second by a factor of 7 times. Well, doing this is quite simpler than to get a magnification of 35 by using a single lens. The ray diagram of a microscope arrangement (given below) shows that the real image created by the first lens is the object for the second lens. Note that the image, which you see while looking through the microscope is the one created by the second lens. Also, note that the final image formed is virtual and inverted in comparison to the original object. Moreover, the same result is true for several types of microscopes and telescopes.

2. Telescope

A telescope is another significant optical instrument. It makes distant objects appear nearer by using an arrangement of lenses or lenses and curved mirrors used to observe the objects by emission, absorption, and reflection of their electromagnetic radiation to provide a magnified image. As the telescopes are used to view objects that are far away, they include at least two lenses. These instruments are designed in such a way that the image created by the first lens is smaller and nearer to its focal length. Moreover, the real and inverted image formed by the first lens is closer to the second lens as compared to its focal length. By using the magnifying glass, the device further gives an enlarged virtual image. The final image formed here is inverted in comparison to the object. However, this thing hardly matters in the case of astronomical telescopes, but when it comes to observing the object which is on the earth, most of us possibly prefer to see an upright or straight image. To get an upright or straight image, the third lens is used.

Conclusion

This article is about optical instruments and their properties. It is specifically designed by our subject matter experts for the better understanding of students. Students can refer to this for a more comprehensive approach towards learning and exams.