Physics subject for your learning

1. FUNDAMENTALS OF PHYSICS
MECHANICS
Matter
 Any substance that has mass and occupies
space by having volume is matter. All objects
that can be touched are composed of atoms.
In simple words, "matter" includes atoms and
anything made up of them, and any particles
that act as if they have both mass and
volume.
 Matter exists in different states such as solid, liquid, and gas – for instance, water exists as ice,
liquid water, and gaseous steam.
 Water as gas is seen in water vapor and the particles move around freely. For both the liquid
and gas, these particles are close together.
 Plasma is defined as a type of gas but the particles are very far apart compared to the other
three states of matter. Plasma can be seen in neon signs.
 Generally we imagine atom as a nucleus of protons and neutrons, and a surrounding "cloud"
of revolving electrons and occupies space. However, this is only partially true, because
subatomic particles and their properties are governed by their quantum nature, which means
they do not act as everyday objects seem to act.
 According to Standard Model of particle physics, matter is not a fundamental perception
because the elementary elements of atoms are quantum entities which do not have an essential
"size" or "volume" in any everyday sense of the word.
Mass & Weight
 Mass is not only a property of a physical body but also
a measure of its resistance to acceleration when a net
force is applied. An object's mass also decides the
strength of its gravitational attraction to other bodies.
 The basic SI unit of mass is the kilogram (kg).
 In physical science, mass is not equivalent of weight,
even though mass is often determined by measuring the
object's weight using a spring scale, rather than balance
scale comparing it directly with known masses.
 An thing on the Moon would weigh less than it does on Earth gravity on the moon is less, but
its mass would be the same.
 Weight is a force, while mass is the property that) determines the strength of this force.
 The weight of an object is related to the amount of force exerted on the object.
 Weight can be defined as a vector quantity, the gravitational force acting on the object.
 Weight can also be defined as a scalar quantity, the magnitude of the gravitational force.

2.  The unit of measurement for weight in the International
System of Units (SI) is the newton. For example, an
object with a mass of one kilogram has a weight of
about 9.8 newtons on the surface of the Earth, and about
one-sixth as much on the Moon. Density
Density
 The density volumetric mass density of an object is its
mass per unit volume. The symbol commonly used for
density is ρ.
 Density is defined as mass divided by volume: p=m/V
where ρ is the density, m is the
mass, and V is the volume.
 In some cases, density is loosely defined
as its weight per unit volume, although
this is scientifically inaccurate – this
quantity is more specifically called
specific weight.
 Different materials have different
densities, and density may be related to
buoyancy, purity and packaging.
Force
 A force is a contact that will change the
motion of an object if it is uninterrupted.
 A force can cause an object to alter its
velocity. Force can also be described as a
push or a pull. A force has both magnitude
and direction, making it a vector quantity.
 It is measured in the SI unit of newton and
represented by the symbol F.
 According to Newton's second law the net
force acting upon an object is equal to the
rate at which its momentum changes with
time.
 Concepts related to force include: thrust, which increases the velocity of an object; drag, which
decreases the velocity of an object; and torque, which produces changes in rotational speed of
an object.
Surface Tension
 Surface tension is shrinking of fluid surfaces into the minimum surface area possible. Surface
tension helps insects, usually denser than water, to float and slide on a water surface.
 Surface tension results from the greater attraction of liquid molecules to each other. The surface
comes under tension from the imbalanced forces, which is probably where the term "surface
tension" came from.
 Due to the relatively high attraction of water molecules to each other through a series of
hydrogen bonds, water has a higher surface tension (72.8 millinewtons per meter at 20 °C)
than most other liquids. Surface tension is an important factor in the phenomenon of capillarity.

3. Motion
 Motion is the change in position of an object with respect to its surroundings in a given interval
of time. Motion is described in terms of displacement, distance, velocity, acceleration, and
speed.
 If the position of an object is not changing with respect to a given frame of reference, the object
is said to be at rest.
 Momentum is a quantity used for measuring the motion of an object.
 An object's momentum is directly associated with the object's mass and velocity. The total
momentum of all objects in an isolated system does not change with time, as described by the
law of conservation of momentum.
Frictional Forces
 Frictional forces are present
everywhere in our daily life. It is
simply impossible to reduce them
completely. Frictional forces are
equally useful in some situations as
they are a hindrance in others. If you
look for a definition of this term in the
physics text glossary you will find:
A force that resists the relative motion of objects that are in contact with each other.

4.  Frictional forces exist between surfaces of two objects being in contact. Their direction is
always parallel to that surface and opposite to the direction of the intended motion of an object.
It is important to emphasize the word intended as frictional forces exist even if there is no
motion.
 The term surface means much more than the surface of a table, floor, road or any other surface
from our daily life.
 A very important field related to friction is motion of solid objects in the air or in water. In this
case the frictional force is called drag force. In spite of a quite different name the drag force is
also a frictional force and only the mechanism which creates this type of friction is very
different from the one creating the friction between two solid objects.
Work, Energy and Power
 Work and energy are mutually connected and must be considered together as work is often
defined in terms of energy and vice versa.
Work can be generally defined as transfer of energy.
 In physics we say that work is done on an object when you transfer energy to that object. In
one object transfer (gives) energy to a second object, then the first object does work on the
second object.
Energy can be defined as the capacity for doing work.
 The simplest case of mechanical work is when an object is standing still and we force it to
move. Consider a small car with a broken engine in the center of the street. The drive can apply
force, push it and move to the side of the street. The driver transfer energy to the car.
 While the car is in motion (very slow one, but motion) it has energy.
The energy of a moving object is called kinetic energy.
 Work done by a Constant Force―When a force causes displacement of a body, work is done.
By work we means mechanical work, as defined in physics.

5. THERMODYNAMICS
 Thermodynamics is a branch of physics which studies the laws that govern the conversion of
energy from one form to another. It studies the direction in which the energy flows and the
availability of energy to do work.
 It is based on the assumption that in an isolated system there is a measurable amount of energy
called internal energy which is usually denoted by letter U. This is the total energy of this
isolated system and it is a sum of kinetic and potential energy of the atoms and molecules of
the system of all kinds.
 It can be transferred directly as heat to other systems if we “connect” these systems. This
definition of internal energy U excludes nuclear and chemical energy. The value of U can be
changed only if we “remove” the isolation of the system by connecting it to other one. In such
a case we can change the internal energy by transferring among the system:
Mass, heat, or work being done on or by the system
Temperature and Heat
 Temperature and heat are not the same
phenomenon. When we touch a piece of
ice, we feel that it is cold. A glass with
freshly prepared coffee is hot. This we
know without studying physics. We can
distinguish between a glass of just
prepared coffee and one that has stood on
the table for 20 minutes. The temperature
of these glasses is different.
 In other words,
―Temperature is the measure of intensity of hotness accumulated in a body. This is not a
definition of temperature, but rather a description of what temperature is. More precisely, the
temperature of a body is a macroscopic measure of the average speed of the body’s atoms and
molecules.
―Heat is a measure of the quantity of heat energy present in a body. If we have two
containers with hot water, one of volume 1.0 milliliter (milliliter = 10–3
) and the other of
volume 1.0 liter, there is 1000 times more thermal energy or heat in this second one.
 The amount of heat energy “stored” in a body depends on its mass, temperature, and on some
internal property, which is called specific heat.
Heat
 Heat is energy in transfer from a
thermodynamic system by mechanisms
including conduction, through direct
contact of immobile bodies, or through
a wall or barrier that is resistant to
matter; or radiation between separated
bodies.
 When there is a appropriate trail
between two systems with varying
temperatures, heat transfer necessarily
takes place, immediately, and spontaneously from the hotter to the colder system.

6.  Thermal conduction takes place by the stochastic motion of microscopic particles. In contrast,
thermodynamic work is defined by mechanisms that act macroscopically and directly on the
system's whole-body state variables.
 The definition of heat transfer does not require that the process be in any sense smooth. For
example, a bolt of lightning may transfer heat to a body.
Evaporation
 Evaporation occurs on the surface of a liquid when it transforms into the gas state. When the
molecules of the liquid strike, they transmit energy to each other based on the way they strike
with each other.
 When a molecule absorbs enough energy to overcome the vapor pressure, it will escape and
enter the surrounding air as a gas.
 When evaporation takes place, the energy removed from the vaporized liquid will reduce the
temperature of the liquid, resulting in evaporative cooling.
 The evaporation continues until an equilibrium is reached when the evaporation of the liquid
is equal to its condensation.
Transfer of Heat
 Heat transfer is concerned with the generation, use, conversion, and exchange of thermal
energy between physical systems.
 Heat transfer can be classified into different mechanisms like thermal conduction, thermal
convection, thermal radiation, and transfer of energy by phase changes.
 Conduction
 Heat conduction is the direct microscopic
exchange of kinetic energy of particles
through the boundary between two systems.
 When an object is at a different temperature
from another body or its environs, heat
flows so that the body and the surroundings
reach the same temperature, at which point
they are in thermal equilibrium.
 Radiation
 Radiation is the emission or transmission of
energy in the form of waves or particles
through space or through a material
medium.
 Radiation includes electromagnetic radiation, particle radiation, and gravitational
radiation.
 X-rays from medical radiography and muons, mesons, positrons, neutrons and other
particles that constitute the secondary cosmic rays that are produced after primary cosmic
rays interact with Earth's atmosphere.
 Convection
 Convection is transfer of heat due to the large scale movement of molecules within fluids
such as gases and liquids.
 Convection includes sub-mechanisms of advection and diffusion .
 Convection does not occur in most solids because bulk current flows and diffusion of
matter do not take place.

7. LIGHT
 Luminous bodies emit light. Non-luminous bodies do not. Instead, nonluminous objects
usually reflect light. Changing the condition of nonluminous object may make it luminous.
Incandescent bodies emit light when they are heated.
 Light travels in straight lines (except in a strong gravitational field). This is called rectilinear
propagation. The path followed by light is represented by rays. (Rays do not actually exist in
nature. They are geometric constructs used to help explain the behavior of light).
 A beam can be thought of as a collection of rays.
 Transparent objects transmit light (absorbing
and reflecting some as well). Translucent
materials scatter and transmit light, preventing
objects from being seen clearly through them.
Opaque materials prevent light from passing
through them.
 Shadows form when opaque objects are placed
directly in the path of light. A total shadow is
called an umbra. A partial shadow is a penumbra. During a solar eclipse, a total eclipse can be
observed within the umbra of the shadow.
Reflection
 Using simple words reflection is the phenomenon when light is returned after impinging on a
surface. To accept reflection we must accept the wave nature of light, because reflection has
to do with waves. Part of light wave or whole the wave remains at the same medium after the
reflection.
 During reflection the angle between the direction of
motion of the oncoming wave and the perpendicular
to the reflecting surface (angle of incidence) is equal
to the angle between the direction of motion of the
reflected wave and a perpendicular (angle of
reflection).
 When light meets with a mirror is reflected and what
follows is the representation of our image onto the
mirror. What we just described is not the usual
situation, because a mirror is considered to be a perfect surface without convolutions.
 Most of the times light does not meet with such perfects surfaces. An orange of orange colour,
for example, has a surface―definitely not perfect―which reflects the orange component of
"white" light (the "white" light includes all the components of colours), whereas it absorbs all
the other components, the red one, the green one etc. This makes possible the vision. Now we
can say we are talking about specular reflection and the similar phenomenon of diffuse
reflection. Although someone has a certain idea about reflection in his mind, he does not realize
the fact that diffuse reflection is much more critical.
 Another part which has to do with reflection is the phenomenon when light meets surfaces
which can reflect it but they are not flat. The surface of a spoon is the perfect example we all
learnt during school years. The surface of a spoon is not a mirror but at the same time it is
something similar to it.

8.  We generally use two terms to describe such non flat mirrors: The concave mirror which could
be represented by the inner surface of a spoon and the convex mirror which could be the outer
surface. In both phenomena the reflected image appears misshapen. Concave mirrors are
widely used in light telescopes where the light that
reaches the telescope is not enough to represent an
image.
―The concave mirror concentrates the rays to a
single point, thus we achieve the representation.
―On the other hand, we take advantage of convex
mirrors in motorways where a convex mirror offers
a wider field of vision than a usual mirror. The
mixture of concave and convex mirrors are usual at
fun fairs where one could be scared of his
appearance totally misshapen.
 Reflection plays an important role to modern microscopes. Light is successively reflected from
mirrors and at the same time it is magnified. Finally, we are able to take a satisfactory
magnification of the element we examine.
Mirrors and Images
 Images in flat mirrors are of the same size as the object and are located behind the mirror.
 Security mirrors form images that are smaller than the object. We will use the law of reflection
to understand how mirrors form images, and we will find that mirror images are analogous to
those formed by lenses.
 In Figure 1, two rays are shown emerging
from the same point, striking the mirror, and
being reflected into the observer’s eye. The
rays can diverge slightly, and both still get
into the eye. If the rays are extrapolated
backward, they seem to originate from a
common point behind the mirror, locating
the image.
 Using the law of reflection—the angle of
reflection equals the angle of incidence—we
can see that the image and object are the
same distance from the mirror. This is a
virtual image, since it cannot be projected—the rays only appear to originate from a common
point behind the mirror. Obviously, if you walk behind the mirror, you cannot see the image,
since the rays do not go there. But in front of the mirror, the rays behave exactly as if they had
come from behind the mirror, so that is where the image is situated.
 In Figure 2, Rays of light that strike the
surface follow the law of reflection. For a
mirror that is large compared with its radius
of curvature, as in Figure 2a, we see that the
reflected rays do not cross at the same point,
and the mirror does not have a well-defined
focal point. If the mirror had the shape of a
parabola, the rays would all cross at a single
Figure 1
Figure 2

9. point, and the mirror would have a well-defined focal point. But parabolic mirrors are much
more expensive to make than spherical mirrors. The solution is to use a mirror that is small
compared with its radius of curvature, as shown in Figure 2b.
 To a very good approximation, this mirror has a well-
defined focal point at F that is the focal distance f from
the center of the mirror. The focal length f of a concave
mirror is positive, since it is a converging mirror.
 The convex mirror shown in Figure 3 also has a focal
point. Parallel rays of light reflected from the mirror
seem to originate from the point F at the focal distance
f behind the mirror. The focal length and power of a
convex mirror are negative, since it is a diverging
mirror.
 Ray tracing is as useful for mirrors as for lenses. The
rules for ray tracing for mirrors are based on the
illustrations just discussed:
 In figure 3, Parallel rays of light reflected from a
convex spherical mirror (small in size compared with
its radius of curvature) seem to originate from a well-defined focal point at the focal distance
f behind the mirror. Convex mirrors diverge light rays and, thus, have a negative focal length.
―A ray approaching a concave converging mirror parallel to its axis is reflected through the
focal point F of the mirror on the same side. (See rays 1 and 3 in Figure 2b.)
―A ray approaching a convex diverging mirror parallel to its axis is reflected so that it seems
to come from the focal point F behind the mirror. (See rays 1 and 3 in Figure 3.)
―Any ray striking the center of a mirror is followed by applying the law of reflection; it makes
the same angle with the axis when leaving as when approaching. (See ray 2 in Figure 4.)
―A ray approaching a concave converging mirror through its focal point is reflected parallel
to its axis. (The reverse of rays 1 and 3 in Figure 2.)
―A ray approaching a convex diverging mirror by heading toward its focal point on the
opposite side is reflected parallel to the axis.
Refraction
 Refraction is the change in direction of a wave passing
from one medium to another or from a gradual change
in the medium. Refraction of light is the most
commonly observed phenomenon, but other waves
such as sound waves and water waves also experience
refraction.
 How much a wave is refracted is dete rmined by the
change in wave speed and the initial direction of wave
propagation relative to the direction of change in speed.
 Consider a wave going from one material to another where its speed is slower as in the figure.
If it reaches the interface between the materials at an angle one side of the wave will reach the
second material first, and therefore slow down earlier. With one side of the wave going slower
the whole wave will pivot towards that side.
Figure 3

10.  This is why a wave will bend away from the surface or toward the normal when going into a
slower material. In the opposite case of a wave reaching a material where the speed is higher,
one side of the wave will speed up and the wave will
pivot away from that side.
Laws of Refraction
 First law of refraction states that the incident ray, the
refracted ray and the normal to the interface all lie in the
same plane.
 Second law of refraction states that for two given media,
the ratio sin is in r =constant, where i is the angle of
incidence and r is the angle of refraction.
ELECTRICITY AND MAGNETISM
 Electricity and magnetism are strongly related field of physics.
 It is hard to find an example where magnetism exist without electricity and electricity without
magnetism associated with it.
 Any motion of electric charges constitutes an electric current and any electric current is a
source of a magnetic field.
Electrostatics
 Electrostatics is a branch of electricity which deals with
electric charges which are not in motion–they are static. There
are plenty of things to learn about electrostatics and you will
see how many phenomena observed in everyday life can be
associated with electric charges and with static electricity.
 Electrostatics is the branch of physics explaining phenomena
arising due to the existence of electric charges, which do not move–they are static.
 Electrostatics can explain numerous physical phenomena observed in everyday life. With static
electricity it is a subject of extensive studies, which are directed towards eliminating,
controlling or–just the opposite–producing electric charges.
Electric Charge
 The Greeks were the first to discover electricity about 2500 year ago. They found that when a
piece of amber was rubbed with other materials it would attract small objects such as dried
leaves, or straw. The Greek word for amber is electron. The word electric was derived from it
and meant “to be like amber.”
 There are numerous materials which possess a similar property. The explanation of this
mechanics, for example. In mechanics we see the objects, we can measure and “feel” the force
acting on it. Everything is in a macroscopic scale.
 The phenomena of attracting by amber other materials is somehow mysterious. There is no
way to observe any macroscopic change of amber after it is rubbed. We must use our
imagination and propose some “mechanism” or model for such behavior.
 Any net electric charge present in nature is always a multiple of the unit charge associated with
an electron (only the sings may vary). The effect of the existence of electric charges can be
observed everywhere. If you walk on a carpet in dry weather and then you bring your finger

11. close to a metal doorknob you produce a spark between the finger close to a metal doorknob
you produce a spark between the finger and the metal.
Magnetism
 Similarities which scientist observed between
electricity and magnetism led them to suggest that
magnetic properties are possibly the result of forces
between electric charges in motion.
 Substances which can be induced to become
magnetized in a magnetic field are called
ferromagnetic. Soft ferromagnetic materials become
demagnetized spontaneously when removed from a
magnetic field. Hard ferromagnetic materials can
retain their magnetism, making them useful in the
production of permanent magnets.
 A compass is a magnet which can align itself within the
earth’s magnetic field. A magnet contains a north–seeking pole (north pole) and a south–
seeking pole (south pole).
 Similar magnetic poles repel. Opposite magnetic poles attract. (Law of Magnetic poles)
 A magnetic field is a region in space where a magnetic force can be detected. The magnetic
field is strongest at the poles of a magnet.
 Magnetic lines of force are a way of representing a magnetic field. The magnetic poles of the
earth are not located at the geographic poles.
 The angle between the geographic North Pole and the magnetic “north” pole is called the
magnetic declination. The angle of declination depends on ‘one’s location of earth.
All copyrights to this material vests with IMS Learning Resources Pvt Ltd. No part of this material either in part or as a whole
shall be copied, reprinted, reproduced, sold, distributed or transmitted in any form in any form or by any means, electronic,
mechanical, photocopying, recording or otherwise, or stored in any retrieval system of any nature without the permission
of IMS Learning Resources Pvt Ltd., and any such violation would entail initiation of suitable legal proceedings.