PHYSICS 9

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Physics is the branch of science concerned with the properties and interactions of matter, energy, space and time.

It explains ordinary matter as combinations of a dozen fundamental particles (quarks and leptons), interacting through four fundamental forces. It describes the many forms of energy (such as kinetic energy, electrical energy, and mass) and the way energy can change from one form to another. It

describes a space-time and the way objects move through space and time.

“An understanding of universe begins with an understanding of physics.”

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PhysicsClassical Physics Modern Physics

Mechanics

Electricity & Magnetism

Thermodynamics

Optics

Atomic Physics Nuclear Physics

Condensed Matter Physics

The study of the motion of objects

The study of heat and the movement of energy

within a system

The study of the electric charges and magnetic

properties of matter

The study of the behaviour and properties of light, including its interactions with matter and the construction of instruments that

use or detect it

The field of physics that deals with the macroscopic physical properties

(optical, electrical, magnetic and elasticity) of matter

It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change

The branch of physics concerned with the nucleus of the atom

PHYSICS 9

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Before 20th century

Beginning of 20th century to present day

Aristotle taught that all things are made up four “elements” :

earth, air, fire and water. Among those who held this view were Democritus and Epicurus. Both view-points

were supported by complete systems of logic.

Galileo Galilei studied the behaviour of falling bodies and formulated laws describing this behaviour. He also investigated the pendulum and put in to use

in a clock.

Kepler discovered that the orbits of the planets were elliptical in

shape and that their motion could be generalised in the form of a mathematical formula that

could be used predict their future motions.

Newton developed the laws of motion and gravitation that

explained the observations of many scientists who had

preceded him. He also made basic discoveries concerning the nature and composition of

light.

During the 18th century, the scientific study of heat and

electric energy. Franklin and Faraday did much of the pioneer

work in electricity, while Rumford and Joule put the study of heat on a scholarly

basis.

With the brilliant work of Maxwell in electricity and

magnetism, physics was further simplified into only two main parts: motion (which includes

heat and sound) and electromagnetism (which

includes light).

In19th century, the study of light was further advanced by the work of Young and Fresnel.

then it became apparent that the various topics of physics (motion, light, electricity, heat

and sound) could all be described in terms of energy.

The discovery of X rays and radioactivity showed that matter was not as simple as had been supposed. The speculations of

Einstein about the laws of motion and the relationship between matter and energy made it

necessary to re-examine the whole structure of physics.

Ernest Rutherford fired very small particles, emitted in radioactive

decay, at a thin film of gold. From the scattering pattern of the

particles, he determined that the atom consisted of a small, heavy,

positively charged nucleus surrounded by very light electrons.

Planck and Einstein in 1913 to explain why the light from gas discharges was emitted at only a few, discrete frequencies; this light formed emission “lines” of different colours when the light was passed through a slit and

dispersed by a prism.

Heisenberg proved that it was impossible to determine both a

particle’s position and momentum with arbitrary

precision; if one is known very accurately, then the uncertainty

in the other becomes large.

Perhaps the greatest such unification that has taken place in this century is the integration of electromagnetism and quantum

mechanics, in quantum electrodynamics (QED). This feat earned Richard Feynman, Julian

Schwinger, and Sin-itiro Tomonaga the Nobel Prize for physics in 1965.

While the basic laws of physics were being studied, man was quick to put these discoveries to use. These applications of science to human needs is known as technology. For example, the development of the laws of planetary motion is a part of pure science. The use of these laws in the manipulation of a spaceship,

on the other hand, is form of technology.

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The science of modelling the universe around us, and then examining and manipulating those models so that we better understand how the

universe works.

The discipline of applying physics models to the real world in order to accomplish a desired

result.

The product, or perhaps the result of physics and

engineering.

Physics

Engineering Technology

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Snell’s lawLaw of Refraction

TelescopeUses the laws of refraction

Space Telescope helps us to

understand the universe

A simple example for the relation between physics & technology.

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PhysicsChemistry Biology

Astrophysics

Geophysics

Interaction of energy and matter in chemical systems. All of the earliest chemists were actually physicists working on particular projects. The forces between chemical bonds, the rotation of electron around nucleus,

electroplating, electrolysis, and electrochemistry all are explained with

the help of physics.

The principles or laws of physics. For example, the circulatory system,

respiratory system, excretory systems are all explained with the pressure, the

muscular – skeleton system is explained with the help of force

concept.

Study of the composition of astronomical objects and the changes that they undergo.

The physics and chemistry of the Earth’s dynamic

processes.

Physical Chemistry

Study of the physical nature of the chemical molecules

Biophysics

concerned with the physical properties of molecules essential to living

organisms.

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Mathematics is the language of physics that has been expressed by Galileo as “Mathematics is the language in which God wrote the Universe”.

Galileo Galilei

Mathematics plays a role in physics that is great way to get a very concise statement that would take a lot of words. For example,

“The speed of an object is calculated by dividing distance to time”.

This expression is written as “v = x / t ”.

To a physicist both expressions say the same thing. The symbols of mathematics replace a lot of words.

The mathematical expressions show the relationship among the variables or we can use the rules of mathematics to change the expressions such as

“x = v.t ”.

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Mass Length Time

Temperature

Electric Current

Luminous Intensity

Amount of matter

kilogram (kg) meter (m) second (s)

kelvin (K)

ampere (A)

candela (cd)

mole (mol)

Every idea in physics is explained in terms of fundamental ideas

called “Basic Units”. Basic units are used to derive, “Derived Units”.

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Table-1.2 Examples of SI derived units.

Quantity Name Symbol

area square meter m2

volume cubic meter m3

speed, velocity meter per second m/s

acceleration meter per second squared m/s2

force newton kg.m/s2

energy joule kg.m2/s2

pressure pascal kg/m.s2

magnetic field strength tesla kg/A.s2

density kilogram per cubic meter kg/m3

power watt kg.m2/s3

Derived units obtain their meaning from the original definitions of the basic units. Therefore, the definitions of basic units are the source of all knowledge in physics.

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Table-1.4Decimal submultiples of SI prefixes.

Factor Name Symbol10-1 deci d10-2 centi c10-3 milli m10-6 micro µ10-9 nano n10-12 pico p10-15 femto f10-18 atto a10-21 zepto z10-24 yocto y

Table-1.3Decimal multiples of SI prefixes.

Factor Name Symbol1024 yotta Y1021 zetta Z1018 exa E1015 peta P1012 tera T109 giga G106 mega M103 kilo k102 hecto h101 deka da

PHYSICS 9

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PHYSICS 9

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The most useful observations are those that can be expressed precisely in terms of numbers.

Such observations are obtained by measurement.

Table-1.5Physical quantities & measuring instruments.

QUANTITY MEASURING INSTRUMENTS

Mass

Time

Length

Temperature

Current

Equal-Arm Balance Digital Scale Bathroom Scale

Measuring Tapes Ruler

MercuryThermometer

DigitalThermometer

BimetalicThermometer

Multimeter Analog Ammeter

Sandglass Chronometer Watch Sundial

In the physical sciences, quality assurance, and engineering,

measurement is the activity of obtaining and comparing physical

quantities of real-world objects and events. Established standard objects and events are used as

units, and the measurement results in a given number for the

relationship between the item under study and the referenced

unit of measurement.

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MeasurementMeasurement is the process of estimating the magnitude of an object, or

comparing the magnitude of object with standards.

Direct Measurement Indirect Measurement

Compare similar quantities of the same dimension.

Compare different quantities, or make some calculations for the result.

Measuring the length of a pencil with a ruler, measuring mass of the stone with an equal-arm balance and measuring the time of flight of a parachutist with a chronometer are all examples of direct measurement. To measure all these physical quantities different kinds of

measuring instruments are used.

Measuring the distance covered by a runner and the time to cover that distance are needed

to calculate the speed of the runner or measuring the mass of an object and its

volume are necessary to calculate the density of that object. These could be examples of

indirect measurement.

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As used by scientists, the word precision refers to the reproducibility of a series of measurements. When several measurements of the same quantity are close to each other, they are said to have good precision. Suppose that three students each use a meter stick to measure the length of a room, and

they get the following measurements:

Student A’s measurement : 10,94 meters Student B’s measurement : 10,93 meters Student C’s measurement : 10,93 meters

Because all three measurements are close to each other (the first differs from the others by only 0,01 meter), the measurements can be described as

having good precision or as being precise.

As used by scientists, the word accuracy refers to how close a measurement is to a true or accepted value. For example, the boiling point of pure water at sea level is

known to be 100 oC. Suppose a student’s measurement of the boiling temperature of pure water at

sea level is 99,9 oC. Because this temperature is very close to 100 oC, you

can say that the student’s measurement is accurate or has good accuracy.

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A series of measurements can be precise without being accurate. For example, suppose that the meter stick used by the three students to measure

the length of the room was defective. Perhaps the manufacturer made an error when marking the scale, or the end of the meter stick had become worn down

after years of use. Then, all three measurements might be inaccurate even though they show good precision.

When several measurements of the same thing are precise but inaccurate, the case often can be traced to the use of a defective measuring instrument.

The precision is good, but the accuracy is poor.

Both the accuracy and precision are poor.

Both the accuracy and precision are good.

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Even when we try to measure things very accurately, it is never possible to be absolutely certain that the measurement is perfect. The errors that occur in

measurement can be divided into two types, random and systematic.

Random Errors Systematic Errors

Random errors can be reduced by repeating the measurement many times and taking the average, but this process will not affect systematic errors. When

you write up your practical work you need to discuss the errors that have occurred in the experiment.

Systematic errors are due to the system or apparatus being used. Systematic errors can often be detected

by repeating the measurement using different method or different apparatus and comparing the results. A

zero offset, an instrument not reading exactly zero at the beginning of the experiment, is an example of a

systematic error.

Some examples of random errors: Changes in experimental conditions, such as

temperature, pressure or humidity. A different person reading the instrument.

Malfunction of a piece of apparatus.

Some examples of systematic errors: An observer consistently making the same mistake.

Apparatus calibrated incorrectly.

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Errors are also expressed as either absolute or relative errors. Absolute error is the actual difference between the measured

value and the accepted value.

Absolute Error (AE)

Measured Value (MV)

Accepted Value (AV)

= -

In laboratory work involving measurements, absolute errors are usually called experimental errors. Notice that the absolute

error carries with it the same unit that was used in the measured and accepted values. Also the sign of the error

shows whether the measured value was above or below the accepted value.

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Relative error is expressed as a percentage, and it is therefore often called the percentage error.

It is calculated as follows:

Absolute Error(AE)

Accepted Value(AV)

Relative Error = .100

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Physics is a mathematical science. The mathematical quantities which are used to describe the motion of objects can be divided into two categories. The quantity is either

a scalar quantity or a vector quantity. These two categories can be distinguished from one another by their distinct definitions:

PHYSICAL QUANTITIES

Scalar Quantity Vector Quantity

Quantity that has a number with its appropriate unit

(magnitude).

Quantity that has a number with its appropriate unit

(magnitude) and a direction.

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Examples of scalar quantities Examples of vector quantities

Mass Force

Volume Weight

Density Velocity

Length Acceleration

Distance Displacement

Speed Momentum

Temperature Electric field

Energy Torque

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Vector quantities are represented by vectors. A vector is a straight line with an arrow at one end. The direction of the arrow represents the direction of the vector and the length of the line represents the magnitude of the vector. Vectors are represented symbolically either with an arrow on top of the symbol or in bold type. Thus, either or “A” respresents a vector, and its magnitude is denoted by .

line of actionmagnitude

Aapplication point

A

AA