Self-explanatory Notes of Grade IX level Physics: Conceptual and Short answers for scoring in board and entrance exams
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| Clear your concepts on Physical Quantities and Measurements From the Notes Library of H.E.S (Health, Education, and Skills) |
Define and explain the word Physics. Briefly discuss the scope of Physics.
Definition of Physics
The branch of science that deals with the study of properties of matter, energy, and their mutual relationship is called physics.
(OR)
The branch of science that deals with the study of the physical universe: energy, matter, and how they are related; is called physics.
Explanation
We (human beings) are always interested in finding answers to fundamental questions, like, how did the universe begin? What is our origin and where is our existence in this universe? How does heat flow from hot to cold bodies? Why moon changes its shape during the month? What is inside the sun to make it too hot? etc. Physics is all about trying to answer questions like these.
Scope of Physics
Physics deals with the world around us, the world inside us, and the world beyond us. Thus the scope of Physics ranges from sub-atomic particles (electron, proton, and neutron) to the largest galaxies and then to the universe. Physicists are concerned with the motion of electrons and rockets, the energy in the sound waves and electric circuits, and the structure of protons and of the universe.
Elaborate on the statement “Mathematics- The language of Physics”.
Mathematics- The language of Physics
Physics describes how the natural world works, through mathematical formulas. In our daily language, we have one word for different meanings, so we often confuse the discussion of ideas. On the other hand, mathematical equations express scientific ideas more clearly, without any confusion. Therefore, findings in nature can be verified or disproved (by experiments) only, when they are mathematically represented.
How technology is shaped by Physics?
Physics in relation to technology/ Link between Physics and Technology
Physics gathers and organizes knowledge about matter and energy. This knowledge is then applied for practical purposes in the form of technology. So they are closely related as well as different from each other. In the modern era, we have biotechnology, electrical technology, satellite technology, civil technology, rocket technology, etc. all of these work on the principles of Physics.How does Physics play a crucial role in science, technology, and society?
Physics and Science
Physics is second only to mathematics in the purity of its principles. Most of the major developments in Chemistry, Biology, Geology, Agriculture, Environmental science, Astronomy, Engineering, and even medicine have been made by physicists.
Physics, technology, and its impact on society
Physics gathers and organizes knowledge about matter and energy. This knowledge is then applied for practical purposes in the form of technology. So technologies work on the principles of Physics. Therefore, Physics has a key role in the progress and improved standard of living of mankind and so strongly affects society.
Following are some examples that describe how Physics and technology affect society.
1. Physics helps in defending a country
Atom bombs are the invention of Physics which is used for the defense of a country as well as for producing a large amount of energy. For example, 1 kg of Uranium produces as much energy as can be produced from burning 30,00,000 kg of Coal.
2. Physics invents instruments for life
Physics approves our quality of life because it provides a basic understanding for developing new instruments in the medical field such as- Computer tomography(CT Scan)
- Magnetic resonance imaging (MRI)
- Ultrasound imaging
- Laser surgery etc.
3. Physics helps us in communication
Physics made communication easier and faster because of improved satellite technology. The combination of mobile cell phones and hologram technology (3D imaging created with photographic projection) greatly affects our society.
4. Electrical appliances are gifts of Physics
Computers, AC, capacitors, inductors, transformers, etc. are those gifts of Physics without which our work becomes loaded and life will be uncomfortable.State the importance of Physics in the light of a few verses of the Holy Quran.
Importance of Physics in the light of Quraan
It is generally accepted that more than 700 verses of the Holy Quran dealing with natural phenomena. The importance of Physics in the light of the Quran can be observed in the following verses.
1. About planets and stars
“And it is HE, who created the nights and days,
the sun and the moon all in their orbits are swimming”
2. About the expansion of the universe
“The heaven WE have built it, with power verity,
WE are expanding it”
3. About the formation of rain
“Have you not seen, how ALLAH drives along the clouds,
then join them together, then make them into the stack
and then you see the rain come out of it”.
4. About the sky as a “protected roof”
“And WE made a heaven sky a well-protected roof yet still;
they turn away from OUR signs”.
Write down the contribution of Muslim scientists in the field of Physics. (Attempted in 2011)
Contribution of Muslim scientists to Physics
Following are some of the contributions of Muslim scientists in the field of Physics.1. Yaqub Kindi
Year of death: 873 AD
- He has a lot of research monographs on meteorology (study of weather), specific gravity, and tides.
- His important work is in the field of optics (light), especially on reflection of light and geometrical optics.
- He also did valuable work in the field of medicine.
2. Ibnal Haitham
Year of birth: 965 AD
Year of death: 1039 AD
Ibnal Haitham was born in Basra (Iraq), following are the some of his contributions.
- He was a great scholar of Physics, mathematics, engineering, astronomy, and medicine.
- On Optics, his masterpiece book is Kitab-ul-Manazir.
- In Kitab-ul-Manazir, the most wonderful chapter is on the human eye.
- He constructed a pinhole camera for imaging the solar eclipse.
- He presented two important laws of reflection.
3. Al-Beruni
Year of death: 1048 AD
Al-Beruni was a famous Afghan scholar; the following are some of his contributions
- He wrote 150 books on mathematics, religion, geology, chemistry, cosmology, archaeology, and history.
- He discussed the shape of the earth, movement of the sun and moon, phases of the moon, and movements of planets.
4. Professor Dr Abdussalam
Year of death: 21 Nov 1996
Dr. Abdussalam was born in Jhang and studied in Govt college Lahore. Following are his contributions.
- He was the first Pakistani scientist who was awarded the Nobel prize in Physics in 1979 for his work on electroweak unification theory.
- He established the international center for Theoretical Physics in Trieste, Italy.
5. Dr. Abdul Qadir Khan
Year of birth: 1936Dr. Abdul Qadir Khan was born in Bhopal, India, and got his Ph.D. from Leven University Belgium. Following are his contributions.
He served as an expert with the collaboration of the Govt of Holland in the Urenco Enrichment plant. In appreciation of his services, the Engineering Research Laboratories Islamabad was renamed A.Q Khan Laboratories.
Define and explain the term Physical quantities. What are its types? (Attempted in 2014)
Physical quantities
Those quantities which are measurable are called Physical quantities.
Explanation
The thickness of our hair, the volume of a liquid, the mass of the earth, the length of a book, etc. are physical quantities because they can be measured. If we write 10, it is a number but if we write 10 kg then it is a physical quantity.
Expressing physical quantities
To express any physical quantity, we must have
a. Magnitude: A number with an appropriate unit is called magnitude e.g. in 10 kg, 10 represents magnitude.
b.Unit: The standard with which things are compared is called Unit e.g. in 10 kg, the unit is kg(kilogram).
Types of Physical quantities
Physical quantities are divided into the following two types
1. Base physical quantities
Those minimum number of physical quantities and their defined and standardized units in term of which all other physical quantities can be expressed are called Base physical quantities.
Base physical quantities are seven in number which are
Length, Mass, Time, Electric current, Temperature, Luminous intensity (intensity of light), and amount of a substance.
The corresponding units of base physical quantities are called base units.
2. Derived physical quantities
The physical quantities defined in terms of base quantities are called derived physical quantities.
Explanation
Speed is an example of a derived physical quantity because it is obtained by dividing one base quantity by another e.g.
Speed = (Distance (Base quantity)) / (Time (Base quantity)) = S/t
The corresponding units of derived physical quantities are called derived units.
Write a short note on the International System of Units. (Attempted in 2012)
International system of units
A complete set of units for all physical quantities is called a system of units.
SI is the short form for an international system of units, which is actually taken from the French name "System international d' units". The international system of units is based on seven base physical quantities from which all other units are derived substances. These have properly defined units of meter, kilogram, second, ampere, Kelvin, candela, and mole.
Following are the systems of units
- F.P.S (foot-pound-second) system.
- M.K.S (meter-kilogram-second) system.
- C.G.S (centimeter-gram-second) system.
Write a short note on
(i) SI Base units (ii) SI Derived units
i. SI Base units
The standardized and defined units of seven base physical quantities are called SI base units.
Explanation
There are seven SI base units i.e. meter (m),
kilogram (kg), second (s), ampere (A),
kelvin (K), mole (mol), and candela (cd).
These are actually the units of seven base physical quantities. Each SI base
unit is defined, standardized, and unique which facilitates accurate and
reproducible measurement.
ii. SI Derived units
Those units which are obtained by multiplying or dividing one SI base unit with another SI base unit are called SI-derived units.
Explanation
Consider the following example in which a unit of speed is obtained by division of two SI base units
Unit of Speed = Unit of Distance / Unit of Time = (m
(SI base unit)) / (s (SI base unit) )
Or ms-1 (a derived unit)
In some derived units, one SI base quantity may involve (شامل) more than once e.g.
Unit of Area = unit of length x unit of breadth
unit of Area = meter × meter = m×m= m2
For simplicity; commonly used derived units are given special names. For example, the SI-derived unit of Force is kgms-2 but this unit is commonly known as Newton.
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Seven base physical quantities and
their SI units |
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|
Base
quantity |
SI
Base units |
||
|
Name |
Symbol |
Name |
Symbol |
|
Length |
l,
x, r (etc.) |
Meter |
M |
|
Mass |
M |
kilogram |
Kg |
|
Time |
𝑡 |
Second |
S |
|
Electric current |
I
or i |
Ampere |
A |
|
Temperature |
𝑇 |
Kelvin |
K |
|
Luminous intensity (Intensity of light) |
𝑛 |
Candela |
Cd |
|
Amount of substance |
I |
Mole |
Mol |
|
Some derived units for ‘International System
of Units’ |
|||
|
Derived Quantity |
SI derived Unit |
||
|
Name |
Symbol |
Name |
Symbol |
|
Volume |
V |
cubic meter |
m3 |
|
Force |
F |
Newton |
N = kg ms-2 |
|
Pressure |
P |
Pascal |
Pa = kgm-1 s-2 |
|
Work, Energy |
W |
Joule |
J = kgm-2 s-2 |
|
Speed, Velocity |
V |
meter-per-second |
ms-1 |
|
Density |
Ρ |
kilogram-per-cubic
meter |
kgm-3 |
|
Area |
A |
square meter |
m2 |
|
Acceleration |
A |
meter per
second square |
ms-2 |
|
Capacitance |
C |
farad |
F= kg-1 m2 s4 A2 |
|
Resistance |
R |
ohm |
Ω=kgm2 s-3 A-2 |
What do you mean by standard form or scientific notation? What are the steps required to change a number into scientific notation? Explain your answer with suitable examples.
Standard form/ Scientific notation
The method of expressing a very large or very small number in the power of 10 is known as standard form or scientific notation.
Explanation
In physics, we mostly deal with either very large or very small numbers. Such numbers can be written in standard form i.e. as the product of a number greater than 1 and less than 10 (called “Mantissa”) and a power of 10 (called “exponent”), so this way of expressing (ظاھر کرنا) numbers is called scientific notation.
The mathematical form of scientific notation
N = M x〖10n〗
Where N = very small or very large number,
And M = number whose first digit is non-zero,
While n = power of 10.
Example 1:
The
mass of moon is approximately 70,000,000,000,000,000,000,000 kg. This number can
be written in standard form/scientific notation as
N = M x 〖10n〗
Here N
= 70,000,000,000,000,000,000,000
kg,
M = 7 and 〖10n〗= , so
N=〖7 x 1022〗kg is the scientific form of 70,000,000,000,000,000,000,000 kg.
Rules for writing a number in scientific notation
In a given number N, move the decimal point and place it after the first non-zero digit which will make it mantissa (M), then follow the rule for
1. Positive power of 10
If the decimal is moved toward the left from its given initial position, then the power of 10 will be positive.
For example,
150,000,000,00 m can be expressed in scientific notation as
1.5 x〖1010〗m
2. Negative power of 10
If the decimal is moved toward the right from its given initial position, then the power of 10 will be negative.
For example
0.000,000,000,000,0016 m can be expressed in scientific
notation as
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