Category: Physics Notes PPT

In the statement of Newton’s first law, the unbalanced force means the force that does not become balanced by the other individual force. If all the up and down forces do not cancel each other and/or all the horizontal forces do not cancel each other, then there is an unbalanced force. It is commonly accepted that there is the ‘net force’ acting upon the object. The net force is the sum of all forces, considering the fact that a force is a vector and two forces of equal magnitude and opposite direction will cancel each other. 

Students who are looking for the best study materials to study and get well-versed with the subject of physics should try out our range of study materials for physics.

On this page, students can find study notes on the topic of the Net Force Formula. This topic is one of the most highly crucial topics in physics. This topic even has a lot of importance from an examination point of view. In other words, studying from this topic can help students get good marks or high rank in the examination or any test. 

Students can get a profound understanding of this topic by learning from the study notes provided by us. The solutions and explanations provided in these study notes are completely relevant and up to date. That is because these study materials are created by us with the help of subject experts on this topic. These subject experts are highly qualified and have a job of huge responsibility at our website. 

The topic of Net Force Formula is a highly important formula for students to learn and get well-versed with. The formula is used in many real-life examples. 

 

Net Force Equation 

If N is the number of forces acting on the body, the net force formula is given by

FNet = F1 + F2 + F3 ….+ FN

Where F1, F2, F3 as forces acting on a body.

When a body is at rest, the net force formula is given by

FNet = Fa + Fg

Where,

Fa = Applied force and

Fg = Gravitational force.

Net force is when a body is in motion and many forces are active on it like gravitational force Fg, frictional force Ff, and the normal force.

Therefore, the net force formula is given by

FNet = Fa + Fg + Ff + FN.

 

Some Examples in Net Force Equation Physics

Example 1

In a game of rope pulling,  a fat man pulls with a force of 100 N from one side, and a lean man pulls with 90 N from the other side. What will be the net force?

Solution:

Given

Force F1 = 100 N and

Force F2 = 90 N

The net force formula is given by

FNet = F1 + F2

FNet = 100 + (-90)

FNet = 10 N.

Therefore, the net force is 10 N.

 

Example 2

A truck is standing still and a force of 70 N is applied on it. If the frictional force is 20 N, then what will be the net force?

Solution:

Given

Applied force Fa = 70 N

Frictional force Ff = 20 N

The net force formula is given by

FNet = Fa + Ff

FNet = 70 + (-20)

FNet = 50 N

Therefore, the net force is 50 N.

 

Conclusion

Newton’s first law is very simple and explains the dynamics of a force on the body at rest and in motion accurately. However, according to Newton’s second law, the magnitude net force formula is derived considering the mass of the body and is stated as FNet= ma.    

The conservation of mass is a part of thermodynamics and it is a fundamental concept of physics. According to physics the mass of the substance should always remain constant. Hence, the mass is neither created nor destroyed, but it can modify from one form to another. The mass of any object can be determined by its volume, density, and area it occupies. 

The mass of a liquid substance passing per unit time is termed the mass flow rate. The mass flow rate can also be expressed as the rate of movement of liquid pass through a unit area. Here, the mass flow rate will vary as the density, velocity of the liquid varies. Also, the mass flow rate will increase as the cross-sectional area increases. So, the mass flow is directly proportional to the velocity of the liquid, density of the liquid, and area of the cross-section. The mass flow rate is the movement of mass per unit time. The mass flow rate can be expressed as m and the mass flow can be calculated in terms of  kg/s. 

Mass flow rate equation m = ρVA

Here, 

m denoted the mass flow rate

ρ denotes the density of the liquid.

V denotes the velocity of the liquid

A denotes the cross-sectional area. 

The cross-sectional area of a tube can be calculated as given below. 

Then, 

A = πr2

Here, r denotes the radius of the tube. 

By using the above mass flow rate of the water formula, we can also calculate velocity from mass flow rate. 

Problems Related to Mass Flow Rate 

Problem 1: Calculate the mass flow rate of a given fluid whose density is 700 kg/m3, velocity, and area of cross-section is 40 m/s and 30 cm2 respectively.

Solution:

As per given data

ρ = 700 kg/m3

V = 40 m/s and

A = 30 cm2

    = 0.30 m2

The formula for calculating mass flow rate (m)

m = ρVA

m = 700 × 40 × 0.30

m = 8400 kg/s

The mass flow rate m  for the above-given data is 8400 kg/s

Problem 2: Determine the density of the liquid? The mass flow rate of the liquid is 4800 kg/s. And the velocity and area of the cross-section are 30 m/s and 20 cm2 respectively.

Solution:

From the given values

m = 4800 kg/s

V = 30 m/s and

A = 20 cm2

= 0.20 m2

To calculate the density of the liquid from the above-given values. 

ρ = m/VA

ρ = 4800 / ( 30 * 0.20 )

ρ =  4800 / 6

ρ =  800 kg/m3

The density of the liquid ρ for the above-given data is 800 kg/m3

The two ways for measuring how fast an object or particle is travelling at a given position and time are Instantaneous Speed and average speed. On , you can learn more about the meanings of both types of speed, how to distinguish between Instantaneous and average Speed, and how to calculate instantaneous speed using the formula.

 

We know that the total distance travelled divided by the total time taken equals the average speed for a given time interval. The distance travelled approaches 0 as the time interval approaches zero. The Instantaneous Speed, on the other hand, is the non-zero limit of the distance-to-time ratio. We can also say that Instantaneous Speed at any given time is the magnitude of Instantaneous velocity at that time, to put it another way.

The average speed for a given time span is equal to the distance travelled divided by the total time necessary. As the time window approaches zero, the distance travelled approaches zero. The Instantaneous Speed, on the other hand, is the non-zero limit of the distance-to-time ratio. To put it another way, the Instantaneous Speed at any given time is the amount of instantaneous velocity at that particular time.

 

Instantaneous Speed Formula

The Instantaneous Speed formula is as follows:

Speed(i) =[ frac{ds}{dt}]

• ds here stands for distance

• The time interval is denoted by it.

• The Instantaneous Speed is speed(i).

 

More About the Topic

When we consider how fast or slow a body moves, we encounter the concept of velocity. We somehow associate body displacement with time spent in such displacement. This type of relationship is manifested as instantaneous speed. We will learn about instantaneous speed and the instantaneous speed formula in this chapter.

 

What is Speed?

Let’s know what speed is! Speed is defined as the rate at which an object’s position changes over time. An object’s speed can change as it moves. The speed of an object at a given point in time is referred to as its instantaneous speed. If the position is a function of time, the speed is determined by the change in position as time passes.

 

As the change in time becomes small, the instantaneous speed can be found. Finding the limit of the position function as the change in time approaches zero is required to calculate the instantaneous speed.

 

 

What is Instantaneous Speed?

It is the rate at which an object’s distance changes with respect to time. The speed unit is metres per second (m/s).

 

The instantaneous speed is never less than or equal to zero. A scalar quantity is instantaneous speed. The instantaneous speed of uniform motion is constant. In other words, the magnitude of instantaneous velocity can be defined as at any given time is the magnitude of instantaneous speed at that time. As the time interval becomes very small, instantaneous speed becomes a limit of average speed.

 

How Do You Measure Instantaneous Speed?

 

v = limit as a change in time approaches zero (change in position/ change in time)

 

Instantaneous vs. Average

When a cop pulls you over for speeding, she measures your car’s instantaneous speed, or the speed at a specific point in time as it speeds down the road. ‘Instantaneous’ is derived from the word ‘instant,’ which refers to a single moment.

 

This differs from your trip’s average speed, which takes into account how long it took to complete the entire journey as well as the distance travelled. Be cautious: measuring average speed assumes you moved at roughly the same speed throughout the trip.

 

To compute instantaneous speed, divide a portion of the total distance travelled by time.

 

Difference Between Instantaneous Speed and Instantaneous Velocity

Latent heat is the heat used to convert a solid to a liquid or vapour phase, or a liquid to a vapour phase. The heat of condensation, the heat of vaporization, and so on are some of the names given to it depending on the different phases. The heat or energy consumed or emitted during a phase change of a material is known as latent heat. It may be from a gas to a liquid or from a liquid to a solid and back again. The heat property enthalpy is related to latent heat.

Here, we will learn about latent heat, different types of latent heat along with the formula and dimension of latent heat.

Latent Heat Equation

The latent heat formula is given by,

L = [frac{Q}{M}]

Where,

L = specific latent heat of a substance

Q = amount of heat

M = mass of the substance

Latent Heat Dimensional Formula

Latent heat dimensional formula is given by,

[M⁰L²T⁻²]

Where,

M = Mass

L = Length

T = Time

Latent Heat of Vaporization Formula

The heat absorbed or discharged as matter disintegrates, changing state from fluid to gas at a constant temperature, is known as latent heat of vaporization.

The heat of water vaporization is the most well-known. The heat of vaporization is described as the amount of heat required to convert 1 g of a fluid into a fume without changing the fluid’s temperature.

Heat of Vaporization Formula

The heat of vaporization formula can be written as based on entropy and enthalpy of vaporization, as well as their relationship.

H[_{v}] = [frac{q}{m}]

Where

H[_{v}] = vaporization heat

m = mass of the substance

q = heat

We should note that the latent heat is associated with no change in temperature but a change in state. The disappearance of water has an articulated cooling effect, while the buildup has a warming effect, due to the high heat of vaporization.

The heat of vaporization is similar to the heat of fusion or melting in that it refers to the amount of heat exchanged during a stage change. It is the amount of heat (540 cal g-1) needed to convert 1 g of water to 1 g of water fume in the case of vaporization. During the conversion of 1 g water fume to 1 g water, a comparable amount of heat is exchanged or discharged.

Latent Heat of Fusion Formula

The latent heat of fusion is the heat consumed or discharged as matter melts, changing state from solid to fluid structure at a constant temperature.

Since sea ice and brine will exist together at any temperature and melt at a temperature other than 0C when bathed in a concentrated salt solution, the content of latent heat is complex in the case of sea ice, just as it is in the walls of brine cells when brine cells migrate. The heat absorbed by the material, or the latent heat of fusion formula, is expressed as when m kg of solid converts to a fluid at a constant temperature, which is its melting point.

Q = M x L

Where

L is the substance’s unique latent heat of fusion.

The heat that the material absorbs or releases is expressed as when the temperature of the substance varies from t1 (low temperature) to t2 (high temperature).

Q = mcΔt

Q = mc(t₂ – t₁)

The total amount of heat absorbed or  liberated by the material is

Q = mL + mcΔt

Since the heat energy expected to shift the material from solid to fluid at air pressure during softening is the latent heat of fusion, and the temperature remains constant during the process, the ‘enthalpy’ of fusion is latent heat. The enthalpy shift of some measure of material as it dissolves is the latent heat of fusion.

The real heat of fusion is defined as the enthalpy shift per mole of the matter when expressed in terms of a unit of mass, while the molar heat of fusion is defined as the enthalpy shift per mole of matter.

The inward energy of the fluid state is greater than that of the solid-state. This means that energy must be given to the solid in order to dissolve it, and energy must be discharged from a fluid as it solidifies since the particles in the fluid have a more delicate intermolecular force and therefore have higher potential energy (a sort of bond-separation energy for intermolecular powers).

Solved Examples:

1. If the amount of heat needed for a phase change is 300 kcal, calculate the latent heat of a 5 kg material.

Sol: Given parameters are,

Q = 300 k.cal

M = 5 kg

The formula for latent heat is given by,

L = Q / M

L = 300 / 5

L = 60 k.cal/kg

Hence latent heat value is 60 k.cal/kg

2. At 20°C, a piece of metal has a density of 60g. When immersed in a steam current at 100°C, 0.5g of the steam condenses on it. Provided that the latent heat of steam is 540 cal/g, calculate the specific heat of the metal.

Sol: Let c be the specific heat of the metal.

Heat gained by the metal

Q = mcΔt

⇒ Q = 60 x c x (100 – 20)

⇒ Q = 60 x c x 80 cal

The heat released by the steam

Q = m × L

Q = 0.5 × 540 cal

By the principle of mixtures,

Heat given is equal to Heat taken

0.5 × 540 = 60 × c ×80

c = 0.056 cal/g ⁰C

Hence specific heat value is 0.056 cal/g ⁰C

Hence, we can conclude that The specific latent heat (L) of a material:

• It is a measurement of the amount of heat energy (Q) emitted or absorbed per mass (m) during a phase shift.

• The formula Q = mL is used to describe it.

• It’s commonly referred to as the material’s “latent heat.”

• The joule per kilogramme [J/kg] is the SI unit.

We have all three types of latent heat and dimension of latent heat. We have solved a few example problems.

Ray Optics is also known as geometrical optics. Ray Optics represents a model of optics that describes light propagation in terms of rays. In Ray Optics, an obstruction or barrier is used for interfering with the path along which light propagates under certain circumstances. Ray Optics is not accountable for specific optical effects such as diffraction and interference. This simplification is very well used when the size of the structure with which the light interacts is bigger than the wavelength. Generally this technique is used in explaining the geometrical aspects of imaging, including optical aberrations.

The simplifying assumptions of Ray Optics say that light rays:

• Must propagate in a straight-line path when they are present in a homogeneous medium.

• In some circumstances, must bend or may have to split in two, at the interface between the two different media.

• Must follow curved paths in a medium where the refractive index fluctuates.

• Must get absorbed or reflected.

Laws of Ray Optics

The Ray Optics or the geometrical optics are based upon three laws.

• The law of rectilinear propagation: It says that light travels in a straight line.

• The law of reflection: It states that when a ray of light gets reflected on a surface separating two optical media, the reflected ray remains within the incidence plane. The angle of incidence is same as that of the angle of reflection. The plane of incidence is the plane where the incident ray and the surface normal is present at the point of incidence.

• The law of refraction: It states that when a ray of light is refracted at an interface separating two optical media, the transmitted ray stays within the plane of incidence, and the sine of the angle of incidence gets directly proportional to the sine of the angle of refraction.

Plane Mirror

A ray optics plane mirror is a mirror consisting of a flat reflective surface. When light rays strike the plane mirror, the angle of reflection is equal to the angle of incidence. The angle of incidence is the angle between the surface normal and the incident ray. The surface normal is the imaginary line that is perpendicular to the surface. The angle of reflection is the angle between the surface normal and the reflected ray. A collimated beam of light never spreads out after getting reflected from a ray optics plane mirror except in case of diffraction effects.

The above image shows how the light rays reflect in a plane mirror and produce a virtual image

Preparation

A ray optics plane mirror is made up of using a highly reflecting and polished surface such as a silver or aluminum surface in a process known as silvering. After completing the silvering process, a thin layer of red lead is to be applied at the mirror’s back. The reflecting surface reflects most of the light rays striking it as long as its surface is not contaminated by tarnishing or oxidation. 

Recently, the modern mirrors are being designed with a thin plate glass that prevents and strengthens the mirror surface and prevents the surface from tarnishing. In the past, mirrors were merely flat pieces of polished copper, obsidian, brass, or precious metal. A mirror is made from a liquid such as the elements gallium and mercury, as they are very highly reflective in their liquid state.

Characteristics of Images Formed By Plane Mirror

The characteristics of the images formed by the ray optics plane mirror are:

• The image is always virtual.

• The image is erect and of the same size and shape as the object.

• The distance of the object from the plane mirror is the same as the distance of the image from the plane mirror.

• The image in the plane mirror is inverted, which means when you are raising your left hand, it would appear in the ray optics plane mirror that you have raised your right hand.

Real Image

Some of its properties are:

• A real image is capable of being seen on the screen.

• A real image is always inverted.

• A real image is formed when the light ray, after going through reflection and refraction, meet at the same point.

• A real image is formed when rays of light actually get intersected.

Virtual Image

Properties of a virtual image are:

• It cannot be obtained on the screen.

• A virtual image is always erect.

• A virtual image is formed when light rays appear to meet at a point.

• A virtual image is formed with the imaginary intersection of light rays.

In our day-to-day life, we normally distinguish between sound and noise. In short, we refer to pleasant sequential impressions as sound, while chaotic or obstructive sounds are considered noise. 

There is a fine line between the sound and the noise. For reducing the noise, a sound-absorbing material is helpful. For studying how sound transmission takes place and how to control the noise, we will learn Acoustics. Now, let’s understand what acoustics is.

The word ‘Acoustic’ is derived from the following Greek word: 

1. ‘Akoustika’, which means ‘of or for the hearing/ready to hear’

2.  ‘Acoustic’, which means ‘heard or audible’. 

Acoustics Physics

Acoustics is the arm of science that deals with production, control, transmission, reception, and sound effects. In simple words, acoustics deals with the process of generation, reception, and propagation of sound.

It is that branch of physics that serves the study of mechanical waves in the states of matter (solid, liquid, and gasses) and also with the following things: 

Define Acoustic

We define Acoustic as the science of sound, including its production, transmission, and effects involving biological & psychological effects.

Sound Acoustics

We define sound as the elastic molecular fluctuations in the air or other media that generates a chain reaction (or vibration) by putting the nearest particle in motion. 

If the mixture of sounds creates an unpleasant impression, it becomes hard to distinguish individual sounds with a short reverberation time; such a type of sound is considered noise. To control these unpleasant/chaotic sounds, we must understand the importance of acoustics.

Importance of Acoustics

The techniques/methods we use to absorb undesirable sounds by using soft-porous surfaces is called acoustic protection. 

For example, you are working in the steel industry, and machines are producing large noises. To reduce this noise, what you can do is, insert any soft material into the valves of the machine, then the noise from that machine minimizes. It’s because the smooth and plain surfaces produce large noise and soft-porous materials avoid the echoing of the sound because of which the sound-level reduces. That’s why porous materials are used in noise control industries.

Conditions for Good Acoustics

The conditions for good acoustics are: 

1. Syllable – The syllable should be loud.

2. The Time Between Two Syllables –  It should be the least. It means that the reflection of the previous syllable should be minimum so that the next syllable is audible. 

3. Echo – The adjustment of echoes should be minimum so that the continuity of sounds doesn’t get affected. 

4. Hall – The windows of the building should be opened and must have absorbing surfaces to avoid the prolonged reflection of the sound. 

5. Reverberation – Reverberation means the reflection of the sound. The reflection of the sound should not be small because if it dies before reaching to ears, then the continuity of sounds gets affected. Such a type of condition in which the reflection of sound dies is called the Dead Hall Effect. 

Types of Acoustics

The types of acoustics with their explanation are as follows: 

We have seen multi-story buildings in big cities like Mumbai many times. These buildings are set up (constructed) in such a manner that they absorb earthquakes. The reason is, vibrational controls are installed in these buildings to protect the buildings from these shocks. These controls are used to ground vibrations in railways. 

This acoustics help reduce the noise created in an environment by different modes of transport.

The frequency of infrasounds is less than 20 Hz. They are not audible to human ears. Infrasounds are useful in the following ways: 

            1. Detecting the probability of earthquakes. 

            2. Noticing petrol formation in a particular area.

The frequency of the ultrasound is greater than the human audible limit. The areas where we use ultrasound are as follows: 

            1. In Ultrasound imaging in physics 

            2. Detecting objects M

            3. Measuring distance 

We study musical acoustics to understand how sounds are used to create any music. The places we use musical acoustics include the following areas of study:

            1. Musical Instruments

            2. Music therapy

            3. Human voice

Applications of Acoustics

The application of acoustics is the proper transmission of sound. Initially, the acoustics were used as a noise-controlling device in industries only. However, at present, use in many fields; these are as follows: 

1. Architectural industries

2. Medicine

3. Warfare

 

Acoustic Energy

Acoustic energy is the disturbance of energy, which passes through a material in the form of waves. An example of acoustic energy is sound energy. When sound travels through any medium, it produces vibrations in the form of waves. In other words, we can define acoustic energy as the energy concerned with mechanical vibrations from its components.

Acoustics – A Branch of Science Dealing with Sound

Sound also called acoustics is a form of energy that can be transmitted from one place to another. Sound is a very important part of our existence. Sound is one of the primary ways by which living beings communicate with each other. In our daily lives, we hear various sounds from both living and nonliving things. How can we hear this sound? How is the sound produced? all these questions arise in our minds. Sound is produced when an object Is in motion. For example, when the strings of a guitar, the skin of a drum, the Hanging ball of a bell vibrate, they produce sound. When we talk, if we place our fingers on our throat we can also feel vibrations. When a bell is struck, not only do we hear the sound of the bell but also if you place fingers on a moving bell our hands start shaking. These are examples of vibrations that are produced by sound. A sound is a form of pressure wave created by the vibration of an object. 

In this article, let us study acoustics and types of acoustics in detail.

Science deals with the study of sound, how it is produced, how it is transmitted, its sources, properties, and effects.

Acoustics is the study in physics that deals with the study of sound waves in glasses, liquids, and solids. Initially, acoustics was used only in industries that are based on sound like an auditorium, theater but today, the use of acoustics has spread to numerous areas.

The acoustic wave equation is the fundamental equation that describes sound waves propagation. In liquids, Sound spreads in the form of pressure waves, and in solids, they spread in the form of long length waves or transverse waves.

There are three categories of sound waves: longitudinal or long length waves, mechanical or self-regulatory waves, and pressure waves.

Characteristics of Sound Waves

• Frequency. 

• Amplitude. 

• Timbre. 

• Envelope. 

• Velocity. 

• Wavelength. 

• Phase.

• Loudness

• Pitch

We can see various waves in the diagram below.

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Acoustic Instruments

Any instrument having strings whether they are made of wood or brass is acoustic in nature. Some instruments which are acoustic in nature are pianos, violins, guitars, clarinets, etc. 

Branches of Acoustics

1. Archaeoacoustics – the study of sound within archeology. 

2. Aeroacoustics – the study of noise generated by air movement

3. Architectural acoustics – the science of how to achieve a good sound within a building.