SLO BASED NOTES

Physics Grade 9th

Sheikh Imtiaz
Chapter 1:

PHYSICAL QUANTITIES & MEASUREMENTS

SCIENCE:
The knowledge gained through observation and experimentation is called science.
The word science is derived from the Latin word ‘’scientia’’ which mean
knowledge.
Observation: A statement based on something one has seen, heard or noticed.
(Sight,
smell, touch, taste and hear.)
Experiment: A test under controlled conditions that is made to demonstrate a
known
truth, or to determine the efficacy of something previously untried.
Science is classified into two basic branches:
1. Natural Science
→ (Physical Science, Biological Science)
2. Social Science
→(Economics’, Political Science)
Due to huge increase in the scientific knowledge up till the beginning of 19 th
century,
it was found necessary to classify the study of nature into two main branches as;
(i) Biological sciences
(ii) Physical sciences
Biological Science:
“The sciences which deal with the study of living things are called Biological
sciences. Example: Biology, Zoology, Botany, physiology etc
Physical Science:
“The sciences which deals with the non-living things are called physical sciences”
Example: Physics, Chemistry, Astronomy, Geology etc
MEASUREMENT"
Measurement is the determination of the size/magnitude of something.
The comparison of unknown quantity with some standard quantity of equal
nature is known as measurement

Q 1: How would you define physics? How physics play a crucial role in science
technology and society?
Ans: Physics:
The word Physics has been derived from Greek word Physikos and physis
which mean natural and nature respectively.
Definition:
The branch of science which deals with the study of properties of matter, energy
and their mutual relationship is called physics.
Matter:
Anything which has mass and occupies space is known as matter.
e.g (air, water, rock etc)
Energy:
The simplest definition of energy is "the ability to do work"
Mutual relationship between Matter and energy:
Matter and energy are related by Einstein's well-known formula.
‘’E’’ is the Energy.
‘’m’’ is the mass and
‘’c’’ is the speed of light
c=3x108 m/s
This formula states that mass is basically another form of energy. Matter can be
converted into energy and energy can be converted into mass.
e.g. Burning of wood, Compton Effect, pair production.
Role of Physics in science technology and society:
Physics is at the root of every field of science. Most of the major development in
chemistry, biology, geology, astronomy and even in medicine has been made by
physicists.
Role in Science and technology:
The use of physics in information technology has improved the standards of
communication. Mobile Phones are very important device for telecommunication.
Hologram technology is a three-dimensional image, created with photographic
projection. The telecommunication industry, including the development of the
internet,
has benefited from physics research in telecommunications from radio waves to
fiber
optics cable.
Cathode ray oscilloscope (CRO) is the invention of physics which can be used as
graph plotting device. CRO use in T.V circuit, in computer system in AC, DC
circuits
etc.
Role in society:
The use of basic laws of physics is common in our daily life. From the coldest
refrigerator to the hottest furnace, from the lowest ship to fastest plane, from the
shape of
finest thumb pin to the shape of huge missiles, aeroplane and spacecraft, law and
principle of physics are used.
Physics has very important role in generation of energy. Now a day’s electrical
energy is requirement for all developing nation physics allow generating electrical
energy
from different sources.
Physics is involved in medical diagnostic techniques, such as, X rays,
magnetic resonance imaging (MRI), and ultrasonic blood flow measurements.
Medical
therapy sometimes directly involves physics

Main Branches of Physics:

On the base of new research in physics, physics divided into two parts.
(i) Classical Physics
(ii) Modern Physics
Physics upto 1900 A.D is called “classical physics” or” Newtonian Physics” and
physics after 1900 A.D up till now and onward is called “modern physics”.
Classical Physics:
A branch of physics, which is mainly concerned with the laws of motion and
gravitation of Sir Isaac Newton and James Clark Maxwell’s Kinetic theory and
thermodynamics, is called classical physics.
Modern Physics:
Modern physics is the branch of physics, which is mainly concerned with the
theory of relativity and quantum mechanics. Albert Einstein and Max Plank were
the
pioneers of modern of physics
Classical Physics (Pre 1900 A.D)
1. Mechanics
2. Heat and thermodynamics
3. Acoustic
4. Optics
5. Gravitation
6. Geo Physics
7. Astrophysics/ celestial mechanics
8. Biophysics
9. Electricity and magnetism
10. Hydrodynamics
Etc
Modern Physics (pro 1900 A.D)

1. Quantum Mechanics
2. Relativity
3. Particle Physics
4. Atomic Physics
5. Molecular Physics’
6. Nuclear Physics
7. Electronics
8. Plasma physics
9. Solid State physics
10. Cryo or low temperature physics
11. Field theory
Etc
1. Mechanics
The branch of physics that deals with the study of motion of material objects
under the action of forces.
Examples: Motion of falling object, friction, weight etc.
2. Heat and Thermodynamics
The branch of physics, that deals with the study of transformation of heat energy
into other forms of energy.
Examples: melting and freezing process, steam engines, refrigerators etc
3. Optics
The branch of physics which deals with the nature of light, its propagation,
reflection, refraction, dispersion and the wave properties of light.
Examples: Mirrors, lenses, telescopes, microscopes etc.
4. Electricity and magnetism
It deals with the study of static as well as moving charges and the phenomena that
occurs due to the motion of charges.
Examples: electric charge, electromagnet, etc
5. Atomic physics
The branch of physics, that deals with the structure and properties of individual
atoms.
Examples: Nuclear reactors, isotopes etc
6. Nuclear Physics:
It deals with the structure and properties of atomic nuclei of an atom.
Examples: X-rays, Lasers, CT scan etc
7. Solid State Physics:
The study of specific properties of matter in solid state
Examples:
Crystals, poly crystals, amorphous etc
8. Particle Physics:
It is the branch of physics which deals with the study of elementary particles.
Examples: Quarks, Leptons, photons, bosons etc
9. Plasma Physics:
The branch of physics which deals with the study of plasma state of matter.
Plasma is known as fourth state of matter. It is matter in ionized state.
10. Quantum Physics:
Quantum physics is that branch of physics which deals with discrete, indivisible
units of energy called quanta as describe by quantum theory.
11. Geo Physics:
It is the branch of physics in which we study various physical properties of earth.
Examples: geothermal energy, continental plates etc
12. Astrophysics and Cosmology:
Astrophysics can be defined as a branch of astronomy which is concerned with
the study of universe.
Examples: Stars, galaxies and planets using the laws of physics. Black holes etc
13. Bio Physics:
Biophysics: a branch of science concerned with the application of physical
principles and methods to biological problems.
Examples: MRI, CT scan, radiotracers etc
14. Relativity:
The general theory of relativity is the modern theory, proposed by Albert
Einstein. The central point of the theory is the principle of general relativity,
which states
that all observers, regardless of their state of motion, will see the same laws
of physics operating in the universe.
Examples: Particle acceleration, Nuclear energy.
Q 3. What is physical quantity? Describe its types.
Ans Physical quantity:
Physics is the science of measurement. So Physics deals with the measurable
quantities
Definition: All the quantities that can be measured are called physical quantities.
For example: Distance, mass, time, Area, Volume, etc.
Explanation: All the physical quantities are measurable quantities, so physical
quantities
are expressed in terms of magnitude.
Magnitude:
Magnitude is the number with proper unit.
Unit:
Unit is the standard with which things are compared.
Example: 50kg, 30m, 20s.
In 50Kg, 50 is number and Kg (kilogram) is SI unit of mass. In 30m, 30 is
number and “m”(meter) is SI unit of length, in 20s. 20 is number and “s” second
is SI
unit of time.
There are two types of physical quantities;
1. Base physical quantities
Definition: Those physical quantities which are the simplest standards selected
by the
scientists in terms of which other physical quantities can be expressed.
Base quantities are those quantities on the basis of which other quantities can be
expressed.
Base Physical quantities are seven in number.
SI Base Quantities & Units:

2. Derived physical quantities

Definition: Those physical quantities which are obtained by multiplying or
dividing
the base physical quantities with other physical quantities are called derived
physical
quantities.
For examples :
Force, Area, Volume, speed, acceleration etc.
Force= Mass x Acceleration
Area = length x length (breadth)
Q.4 What is international system of units?
Ans. System of Units:
Definition: A complete set of units, both fundamental and derived for all kinds of
physical quantities is called system of units.
The common systems are:
CGS: The system is also called Gaussian system of units. Basic units in this
system are
(centimeter, gram , second)
FPS: This system was introduced by British. Base unit in this system are:
( foot, pound, second)
MKS: The system is also called Giorgi system. Basic units in this system are
meter,
kilogram and second.
SI: It is known as International system of units. This system was established in
1960.
The system of units in which the unit of length, mass and time is meter, kilogram
and second respectively is called system international (SI).
It is based on seven basic units from which all other units are derived
Q.5 State and explain what is scientific notation?
Ans. Scientific Notation:
Every small or large number “N” can be expressed in terms of number “M”
multiplied by the negative or positive power of 10 as follow:
N (number) = M (mantissa) x10n(exponent)
Where n = 0,±1,±2,±3,±4,…………
Mantissa:
Number greater than 1 and less than 10 called as mantissa.
Importance:
In measurements, sometimes we deal with very small and very large numbers
which are very difficult to repeatedly write in problems. For this purpose, we
write in scientific or standard form.
Rules to write in standard form:
It must be noted that the first digit of “M” from left to the right is non-zero digit.
In a given number N, move the decimal point and place it after the first non-
zero digit.
If the decimal point is moved towards left from its given initial position, then
the power of 10 will be positive.
Similarly if the decimal point is moved towards right from its given initial
position, then the power of 10 will be negative.
For examples The mass of moon is 70000000000000000000000Kg. In scientific
Notation = 7x1022Kg.
The diameter of atomic nucleus is about 0.00000000000001m. In scientific
Notation = 1x10-14m
Q.6 What are prefixes? Explain
Ans. Prefixes
Definition: Smaller or higher units are in power of 10 which are called prefixes.
Prefixes are the word or letters added before SI units such as milli, kilo, centi, deci
etc
Prefixes to power of ten:
A mechanism through which a very small or very large number is expressed in
terms of power of ten it is called prefix to power of ten.
Explanation:
In scientific calculation some time we have to deal with quantities that are either
very large or small compared with the base units, in such cases we use higher or
smaller units of the standard unit.
For examples
The distance between two cities is taken in kilometer rather than in meter.
The thickness of a wire is taken in millimeter rather than in meter.
Q 7 :Write a note on meter rule?
Ans: Meter Ruler:
Definition: Meter ruler is used in laboratory to measure the length of objects or
the distance between two points.
Least count of meter rule:
Meter rule is one meter long which is equal to 100 centimeters. Each cm is
divided into 10 small divisions called millimeter (mm). Thus one millimeter is the
smallest reading that can be taken using a meter rule and is called its least count.
Least Count:
Least count is the minimum value that can be measured on the scale of measuring
instrument.
Error in reading:
One of the most common type of error is called parallax error. Parallax error is
due to incorrect positioning of your eyes.

For accurate measurement:

For accurate measurement the eye must always be placed vertically above the
mark
being read. This is to avoid the parallax error.
For accuracy:
To improve accuracy further, take several readings, and use the average of these
readings
for better result.

Q 8: Write a comprehensive note on Vernier calipers?

Ans: Vernier calipers:
An instrument used to measure small length up to 0.1mm (0.01cm). It can be
used to measure the thickness, diameter or width of an object and the internal,
external
diameter of hollow cylinder.
Invented By:
Vernier caliper was invented by a French mathematician Pierre Vernier in 1631.
Parts of a Vernier caliper:
1. Lower large jaws: used to measure external diameter or width of an object
2. Upper small jaws: used to measure internal diameter of an object
3. Depth probe/Gauge: used to measure depths of an object or a hole
4. Main scale: It has marking of 1mm each and contains a jaw on its left end.
5. Vernier scale: A sliding scale that has marking of 0.9mm each. It has total 10 or
20 divisions. Vernier scale also contains a jaw on its left end
6. S

crew clamp: Is used to fix Vernier scale

Least Count:
Minimum length which can be measured accurately with the help of vernier
calipers is called least count of vernier constant.
To find least count (Vernier constant):
Method 1:
The difference between one main scale division and one Vernier division is called
Vernier constant.
Least Count = One main scale division – One main scale division
Method 2:
This is the minimum length which can be measured accurately with the help of a
Vernier calipers. So it is called least count of Vernier calipers.
The least count of Vernier calipers is calculated by:

When divisions on V.S are 10 = 0.1mm = .01cm

When divisions on V.S are 20
Then Least count = = 0.05mm = 0.005cm
Method to use:
Consider we want to measure the diameter of a small solid cylinder;
First note the least count of Vernier calipers.
Close the jaws of the Vernier calipers and check the zero error.
Fix the solid cylinder in between the jaws of the Vernier calipers and tight the
screw.
Note the reading on the Main scale (MSR).
Find out the coincide division of the Vernier with the Main scale.
Multiply the coincide division with the least count; this is called Vernier scale
reading (VSR).
Add main scale reading with Vernier scale reading, this is the required
diameter of the solid cylinder.
In case of zero error. If there is positive zero error then subtracts it from final
reading. In case of negative zero error, add it in final reading
Q 9: What is zero error in Vernier calipers? How it can be corrected.
Ans: Zero Error:
If the jaws of the Vernier calipers are closed and the zero of the main scale does
not coincide with the zero of the Vernier scale, then there is an error in the
Vernier calipers which are called zero error. There are two types of zero error.
Positive zero error:
When the zero of the Vernier scale remains right to the zero of the main scale, the
error is called positive zero error. The positive zero error must be subtracted from
each reading

Negative zero error:

When the zero of the Vernier scale remains left to the zero of the main scale, the
error is called negative zero error. The negative zero error must be added with
each reading.

Q 10: Write a comprehensive note on Screw gauge?

Ans. Screw gauge:
A micrometer screw gauge is used to measure small lengths or diameter up to
0.01mm or
0.001cm.
Invented By:
Screw guage was invented about 1638 by William Gascoigne, an English
astronomer.
Parts of screw gauge:
1. Anvil and spindle in which object to be fixed.
2. Linear scale which is also known as main scale
3. Circular scale or Thimble scale
4. Ratche

Pitch of the screw:

As, the circular scale completes one rotation, the spindle moves through some
distance along datum line. This distance is called the pitch of the screw.
If numbers of divisions on circular scale are 50 then pitch of screw will be 0.5mm
and if numbers of divisions on circular scale are 100 then pitch of screw will be
1mm.
Least count:
The pitch of the screw divided by the total number of divisions on the circular
scale is called least count of the screw gauge.
Mathematically:

L. C = 0.01mm = 0.001cm

Method to use:
The diameter of small sphere is measured by using a screw gauge by the following
method
Note the least count of the screw gauge.
Check zero error in the screw gauge by closing it.
Place the sphere between the spindle and anvil and close it.
Note the reading on the main scale (MSR).
Find out the coincide digit of the circular scale with the main scale.
Multiply the coincide digit with the least count; this is called circular scale
reading (CSR).
Add main scale reading and circular scale reading, this is the required
diameter of the sphere.
Q 11: What is zero error in screw gauge? How it can be corrected.
Ans. Zero error and its correction:
If the spindle and anvil of the screw gauge are closed and the
zero of the main scale coincides with the zero of circular scale, then
there is no zero error in the screw gauge.
If the spindle and anvil of the screw gauge are closed and the zero of
the main scale does not coincide with the zero of circular scale, then

there is zero error in the screw gauge.

Negative zero error:

If the zero mark of the circular scale remains above the datum line
of the main scale, then the error is called negative zero error which is
added with each reading.

Positive zero error

If the zero mark of the circular scale remains below the datum line
of the main scale, then the error is called positive zero error which is
subtracted from each reading.
Q12: Write note on Physical balance
Ans: Physical Balance:
Physical balance is a measuring instrument use to compare to masses of two
bodies.
Construction:
Physical balance is just a common balance where there are two pans and, we
measure mass of and object by putting it in one pan and known mass in the other.
Least count of Physical Balance:
A physical balance is a very sensitive common balance which can measure mass
in milligram.
Precaution:
Physical balance must place in a protective glass case so that even dust and wind
cannot affect the accuracy of the instrument.

Q 13: Write a note on stop watch?

Ans. Stop Watch:
Stop watch is used to measure duration of time of specific time interval.
Types of Stop watch:
There are two types of stop watch Digital stop watch and Analogue stop watch.
(i) Mechanical / Analogue Stop Watch:
It consist of two hands a small minute hand and long second hand. Scales for
each hand is marked on circular dial.
Method to use:
To note the time both the hand set at zero by
pressing and releasing knob B. As the knob B is pressed
and released again, the watch starts. When second hand
completes two rotations of 30 seconds each, the minute
hand advances by one division. To stop watch press
same button B. After noting the duration of the time the
button B is again pushed, which brings back the hands
on zero position.
Least count:
Le ast count of analogue stop watch is 0.1 sec

(ii) Digital Stop Watch:

Digital stop watch due to their crystal oscillator timing element,
are much more accurate than analogue stop watch.
Method to Use:
The timing function in digital stopwatch is usually controlled by
two buttons. Pressing the top button starts the timer running, and again
pressing the button a watch stops, leaving the elapsed time displayed.
Then press the second button to reset.
Least Count:
Digital stop watch have a least count of 0.01 sec.
So digital stop watch use in physics experiments

Q 14: Write a note on measuring cylinder?

Ans: Measuring cylinder:
Measuring cylinder is used to measure the volume of liquid and irregular objects.
Construction:
Measuring cylinder is made of transparent plastic or glass and has vertical scale in
milliliter (ml) or cubic centimeter (cm3 ).
Measuring Volume of Liquid:
When the liquid is poured into the cylinder, the volume is read from the scale on
the side. To read the volume of the liquid accurately the base of the measuring
cylinder must be placed on flat surface and eye must be leveled with the bottom of
the meniscus.
Meniscus:
The surface of the liquid curves upwards at the point where it touches the inside
of the cylinder. This curvature is called the meniscus.
Measuring volume of irregular object:
Measuring cylinder is also used to measure volume of
irregular object.
Procedure:
Water is poured into a measuring cylinder until the
cylinder is half full. The volume is measured, and then the
irregular object is lowered gently into it. When the object is
completely immersed the volume of the water is read again.
The volume of the object is found by subtracting the first
reading from the second.

Q 15: What is meant by significant figures? How it can be identified.

Ans: Significant figures:
Rane Decortas for the first time explain the concept of significant figure in 1637.
Definition:
It can be defined as “The number of accurately known figures and the first
doubtful figure are known as significant figures.
For example 6.5 have two significant digits. 56.366 Have 5 significant figures.
General rules for significant figures:
1. All non-zero digits are significant (1,2,3,4,5,6,7,8,9) .e.g 563.2cm There are 4
significant figures.
2. Zero may or may not be significant.
(a)Zero between two significant digits also a significant. i.e 24005 has 5
significant digits.
(b)Zeros to the left of a significant digit are not significant. i.e 0.00056 has 2
Significant
digits
Zero to the right of significant may or may not be significant.
(c) In decimal factors, zero to the right are significant. i.e 3.56000 has 6 significant
digits
(d) In non-decimal factor, zeros to the right may or may not be significant,
depends upon
the counting of measuring devise.
i.e
6000kg ------- 1Kg ( least count of devise ) -------- 4 significant digits
6000kg ------- 10 Kg ( least count of devise ) -------- 3 significant digits
6000kg ------- 100 Kg ( least count of devise ) -------- 2 significant digits
3. When a measurement is in scientific notation, the figure other the power of ten
is
significant.
i.e 2.4x106 km has 2 significant digits.
…………………………………………………………………………………………
………
Q 16: How we can round off the significant figures?
Ans: Rules for Rounding off significant figure:
1. If the dropping digit is less than 5 then it will be ignored, there will be no
change in
last retained digit.
Example: 2.6573 is rounded to 2.657
2. When the dropping digit is greater than 5 then 5 then the last retained digit
increases
by. Example: 2.6578 is rounded to 2.658.
3. When the dropping digit is 5 and the last retained digit is even then the last
digit i.e 5
will be dropped without retained digit.
Example:
2.6585 is rounded to 2.658
4. If the last digit is 5 and the last retained digit is an odd then the last retained
digit is
increased by 1 in order to round off 5.
Example: 2.6575 is rounded to 2.658

….………………………………………………………………………………………………………………………………………………………

"When you want really something, all the universe conspires in helping you to achieve it".

Conceptual Questions (KPK Book)

Q1: How technology is shaped by physics?
Ans: Physics and Technology:
Physics and technology are closely related. Physics is concerned with gathering
knowledge and organizing it. Technology lets humans use that knowledge for
practical
purpose. Physical phenomenon is there behind every technology.
For example:
In Information technology, cell phone, optical fibers, hologram technology,
satellites, GPS etc. All based on Physics laws and principles.
In medical MRI , CT scan, X-rays technology is being used.
Physics has important role in designing fast moving trains, aero plans, cars etc.
…………………………………………………………………………………………
…..
Q 2: Physics and biology are considered different branches, how physics likes
with biology?
Ans: Physics:
The branch of science which deals with the study of properties of matter, energy
and their mutual relationship is called physics.
Biology:
Biology is the natural science that involves the study of life and living organisms,
including their physical structure, chemical composition, function, development
and evolution.
Relationship between Physics and Biology:
Biophysics relates physics and biology. Biophysics branch of science concerned
with the application of physical principles and methods to biological problems.
Physics has many applications in the biological sciences. On the microscopic level,
it helps describe the properties of cell walls and cell membranes. On the
macroscopic level, it can explain the heat, work, and power associated with the
human body. Physics is involved in medical diagnostics, prevention and
treatment, such as, X rays, magnetic resonance imaging (MRI), and ultrasonic
blood flow measurements. Medical therapy sometimes directly involves physics:
cancer radiotherapy uses ionizing radiation.
Q 3. Why are measurements important?
Ans: Measurement:
The word measurement is come from Greek word “ metron” which means “
limited proportion” Measurement is comparison of unknown quantity with some
standard quantity of equal nature, known as measurement.
Importance:
Measurement helps us to know about the exact magnitude of the quantity.
Without the ability to measure, it would be difficult for scientists to conduct
experiments. Measurement is important not only in science and chemical
industry, it is also important in engineering, farming, construction etc
Q 4. Why area is called a derived quantity?
Ans. Area is called a derived quantity.
Reason:
Area is the multiple of two base physical quantities length and width. As we
know physical quantities are obtained by multiplying or dividing the base
physical quantities with other physical quantities. Therefore area is known as
derived physical quantity, because area is multiple of two physical quantities.
Mathematically:
Area = length x width
A = Lx W
SI Unit: The SI unit of area is m2
Q 5: Name any four derived units and write them as there base units?
Ans: Derived Units:
Units derived from multiplying and dividing base units are known as derived
Force (F=ma) newton N 1N = Kg m s- 2
Energy (E=mgh) Joul J 1J = Kg m2 s-2

Pressure (P=F/A) Pascal Pa 1Pa = N m - 2

Resistance (R =V/I) Ohm (omega) 1 kgm2s-3 A-2

Q 6: Why in physics we need to write in scientific notation?
Ans: Scientific Notation:
Every small or large number “N” can be expressed in terms of number “M”
multiplied by the negative or positive power of 10 as follow:
N = Mx10 n
Where n = 0,±1,±2,±3,±4,…………
Importance:
In measurements, sometimes we deal with very small and very large number =s
which are very difficult to repeatedly write in problems. For this purpose, we
write in scientific or standard form.
For Example:
Radius of earth is 6400000 m in standard form 6.4 x106m
Q7: What is least count? How least count for vernier calipers and screw gauge
are defined.
Ans: Lest count:
The smallest value that can be measured on the scale of measuring instrument.
1. Least Count of Vernier calipers:
Minimum length which can be measured accurately with the help of vernier
calipers is called least count of vernier constant.
To find least count (Vernier constant):
Method 1: The difference between one main scale division and one Vernier
division is called Vernier constant. Least Count = One main scale division – One
main scale division
Method 2:
This is the minimum length which can be measured accurately with the help of
Vernier calipers. So it is called least count of Vernier calipers.
The least count of Vernier calipers is calculated by:
Least count =
When divisions on Vernier .Scale are 10
= 0.1mm = .01cm
When divisions on Vernier .Scale are 20
Then Least count = 0.05mm = 0.005cm
2. Least Count of Screw gauge:
Minimum length which can be measured accurately with the help of vernier
calipers is called least count of vernier constant.
Calculation for Least Count of screw gauge:
The pitch of the screw divided by the total number of divisions on the circular
scale is called least count of the screw gauge.
Mathematically:
Least count = L.C = 0.01mm = 0.001cm

Q 8. How can we find the volume of a small pebble with the help of measuring
cylinder?
Ans:
Measuring volume of small pebble:
Measuring cylinder is used to measure volume of small
pebble.

Procedure:
Water is poured into a measuring cylinder until the
cylinder is half full. The volume is measured, and then the
small pebble is lowered gently into it. When the small
pebble is completely immersed the volume of the water is
read again. The volume of the small pebble found by
subtracting the first reading from the second.
For Example:
First reading is 50ml and second reading is 75ml
Volume of pebble is 75-50= 25ml or 25cm3
“There are no secrets to success it is the result of preparation, Hard work, and
learning from failure”
(Colin Powell)

Conceptual Questions (PUNJAB Book)

1.3 Pick out the base units in the following: joule, newton,
kilogramme, hertz, mole, ampere, metre, kelvin, coulomb and
watt.
Kilogramme, mole, ampere, metre and kelvin are base units.
1.4 Find the base quantities involved in each of the following
derived quantities:
(a) Speed
(b) Volume
(c) Force
(d) Work
(a) , so base quantities involve in speed are distance and time.
(b) Let . Length, breadth and height all are base quantities.
(c) , here mass is the base quantity.
(d) , here displacement is the base quantity.
1.5 Estimate your age in seconds.
Suppose my age = 15 years = 15 x 365 days= 5475 days = 5475 x 24
hours= 131400 hours = 131400 x 60 minutes = 7884000 minutes =
7884000 x 60 seconds =473040000 seconds.Prepared by: Muhammad
1.6 What role SI units have played in the development of
science?
International system of units (SI) has defined the standards of
various physical quantities. These are called SI Units. SI units
plays important role in the development of science due to the
following properties.
1. SI units of various physical quantities are used all over the
world.
2. The manipulation of SI units is quite easy. i.e. the multiples
and submultiples of different units are obtained by simply
multiplying or dividing by 10 or powers of 10.
1.7 What is meant by vernier constant?
The least count of vernier callipers is called vernier constant. It is
defined as the difference between one main scale division and one
vernier scale division. Its numerical value is 0.1 mm or 0.01 cm.

1.8 What do you understand by the zero error of a measuring

instrument?
If a measuring instrument gives the reading of a measurement more
or smaller than the actual value then there exists a zero error in the
instrument.
For example zero error in the vernier callipers occurs when on
closing its jaws the zero of the vernier scale is not coinciding with
the zero of the main scale. Zero of the vernier scale is either right or
left of the zero of the main scale. In micrometer screw gauge zero error
occurs when on joining the spindle with stud the zero of the circular scale
is not coinciding the index line of the main scale. Zero of the circular scale
is either remains left behind or crosses the index line.Prepared by:
Muhammad
1.9 Why is the use of zero error necessary in a measuring
instrument?
To correct the observed reading of a measurement taken from a
measuring instrument, its zero error must be recorded and then
this error is added to or subtracted from the observed reading. This
is called zero correction.
If there is a positive zero error in the measuring instrument then
this error is subtracted from the observed reading for zero
correction and if there is a negative zero error in the measuring
instrument then this error is added to the observed reading for zero
correction.
1.10 What is stopwatch? What is the least count of a mechanical
stopwatch you have used in the laboratories?
A stopwatch is used to measure the time interval of an event. A
mechanical stopwatch can measure at a time interval up to a
minimum one tenth of a second (0.1 second). So least count of
stopwatch = 0.1 s
1.11 Why do we need to measure extremely small interval of
times?
We need to measure extremely small intervals time to get greater
accuracy in the result of time dependent physical quantities.
1.12 What is meant by significant figures of a measurement?
In any measurement the accurately known digits and first doubtful
digit are called significant figures.
It reflects the precision of measured value of a physical quantity.
1.13 How is the precision related to the significant figures in a
measured quantity?
Greater the number of significant figures in a measured quantity
greater will be the precision. If least count of a measuring
instrument is smaller, it is said
to be more precise instrument and it will give more significant figures on
measurement. For example reading taken by screw gauge is more
precise then the reading taken by vernier callipers. Prepared by:
Muhammad Asim
Quick Quiz [Page No. 4]
1. Why do we study physics?
We study physics:
(i) To understand the natural phenomena happening around us, on the
earth and in the universe.
(ii) To search for the basic rules of behavior of matter and energy on
every scale: from the interaction of subatomic particles, to the motion of
everyday objects, to the evolution of galaxies.
2. Name any five branches of physics.
Physics consists of many sub-fields, including: Particle and nuclear
physics, Atomic and molecular Physics, Optics, Solid state physics,
Biological and medical physics, Acoustics, Astrophysics and
cosmology etc.