Chapter No 1 Physics Notes For Class 9th

UNIT 1: PHYSICAL QUANTITIES AND MEASUREMENT

EXERCISE:

MULTIPLE CHOICE QUESTIONS:

How many millimeters are there in 10 cm? A. 100 mm
Which of the following quantity can be measured using a micrometer? C. Length
The instrument best measures the internal diameter of pipe is: A. Screw Gauge
Which prefix has the largest value? D. exa
Which of the following is smallest prefix? A. atto
Which of the following numbers shows one significant digit? D. 6 x 102
Which of the following numbers shows 4 significant digits? A. 9.008
A light year is distance travelled by light in one year. It travels about 9.460 x 1015m.

How many significant figures are there in this number? D. 4

0.2 mm in units of meter is: D. Both A and B
KITAB UL MANAZIR is the name of book written by: B. Ibnal Haitham

CONCEPTUAL QUESTIONS:

Give a brief response to the following questions.

Q1. How technology is shaped by physics?

Ans: Physics is the name of the rules by which technology plays its role. Physics tends to explain how something in the universe works and technology, in turn, utilizes its discoveries to setup useful materials. For instance

Physics explains “How electrons are emitted from cathode ray tube?” and technology utilizes its answer to make TV tubes.
The principle of reflection and detection of electromagnetic waves led towards the invention of Radar.
The principles of electromagnetic induction are used by the electric power used to generate at power stations.
The automobile technology is based on the principles of thermodynamics.
Solid state physics is the bases of all electronic devices.

Q2. Physics and biology are considered different branches of science. How physics links with biology?

Ans: Physics provides a basis for biology. Without physics, (space, matter, energy, time etc), there would be no concept of life. Following are some of the examples showing the link of physics with biology:

Gravity, a concept explained by physics, affects flow of blood in the body (biology).
Dolphins, bats, and whales use UV-radiations for their movement.
MRI (Magnetic Resonance Imaging) of brain, x-rays of bones, ultrasounds etc are the applications of physics (magnetism and waves).
Plants movements like phototropic, geotropic etc are due to the effects of light and gravity etc, explained by physics.
Greenhouse effect, an invention of physics, is applied for the growth of plants.

Q3. Why are measurements important?

Ans: Measurements help us to better understand the world around us. Measurements help us in several ways by providing a standard for everyday life and processes. . For example:

We need measurements to calculate blood pressure, heart-beat rate.
Proper construction of buildings is due to the proper measurements.
Purchasing and selling of different stuffs are also possible because of measurements.
Weight, temperature, length and even time, concepts we use in everyday life, are all measurements.
Money or currency used in daily life is also measurement.

Q4. Why area is a derived physical quantity?

Ans. Area is a derived physical quantity because it is the product of base physical quantities length and breadth i-e

Area = Length x Breadth

= m x m

= m2

Q5. Name any four derived units and write them as their base units.

Ans. Derived Units; The units which are expressed in terms of base units are known as derived units.

Physical Quantities	SI Units	In terms of base units
Force	newton (kg. m/s2)	kg. m/s . s
Energy	joule (Nm)	kg.m. m/s . s
Acceleration	m/s2	m/s.s
Momentum	kg. m/s	kg. m/s

Q6. Why in physics, we need to write in scientific notation?

Ans: Scientific notation is used in physics to represent very large or very small numbers in a convenient way. It uses powers of ten (m x 10n) to express such numbers that are either very large or very small. For example, speed of light is 299,792,458 m/s, which is a large number, can be expressed as 3 x 108 m/s, which is easy to remember and write. Similarly, the diameter of atomic nucleus is about 0.000000000000001m, which is written as 1 x 10-15 m in standard form or scientific notation.

Q7. What is least count? How least count for vernier caliper and screw gauge are defined?

Ans: Least Count:

The smallest accurate value that can be measured by a measuring instrument is called least count of that instrument. For example the least count of a wall clock is one second.

Least Count of Vernier Caliper:

The smallest length that can be measured by using a vernier caliper is called the least of vernier caliper. It is the difference between the value of one main scale division and the value of one vernier scale division. Least count of vernier caliper is also called vernier constant. It is obtained by dividing “1” main scale division (1 mm) by total numbers of vernier scale divisions which is 10, i-e

L.C = mm = 0.1 mm = 0.01 cm

Least Count of Screw Gauge:

The smallest length that can be measured by using a screw gauge is called the least of screw gauge. It is obtained by dividing pitch of the screw i-e “1” linear scale division (1 mm) by total numbers of circular scale divisions which is 100, i-e

L.C = mm = 0.01 mm = 0.001 cm

Q8. How can we find the volume of a small pebble with the help of measuring cylinder?

Ans: Following are the steps taken to measure the volume of a small pebble with the help of measuring cylinder.

Take a measuring cylinder and pour some water in it.
Record the reading and note it as V1, it gives the volume of water.
Put a pebble of unknown volume into water. Note that water level rises up.
Record the reading again and note it as V2, it gives the volume of both the water and the pebble.
The difference between both the readings () gives the volume of pebble. i-e

Volume of pebble = = V2 – V1

COMPREHENSIVE QUESTIONS

Give an extended response to the following questions.

Q1. Define physics. How physics play a crucial role in science, technology and society.

Ans. PHYSICS:

Physics is the branch of science that deals with the study of properties of physical universe i-e energy and matter, and the mutual relation between them.

EXPLANATION:

Physics plays an important role in understanding the world around us, the world inside us and the world beyond us. It covers a wide range of phenomena, from the smallest sub-atomic particles to the largest galaxies and universe.

ROLE OF PHYSICS IN SCIENCE:

Physics is at the root of every field of science. Most of the major developments in Chemistry, Biology, Geology, Agricultural, Environmental science, Astronomy, Engineering and even in medicine are due to the study of physics.

ROLE OF PHYSICS IN TECHNOLOGY:

Physics deals with gathering knowledge and organizing it and forms the bases of technology which helps humans in using this knowledge for practical purposes. Physical phenomenons are involved behind every technology

ROLE OF PHYSICS IN SOCIETY:

Physics plays a vital role in the progress of humankind and in the improvement of quality of living. From the coldest refrigerator to the hottest furnace, from the ship to airplane, finest thumb pin, huge missiles and spacecrafts are all due to the principles and laws of physics. Some of the important applications of physics for the betterment of human beings are as under:

Physics provides basic understanding for developing new medical instruments and technologies such as x-ray, ultrasound, CT scan, MRI and laser technology.
The study of physics in information technology has improved the standard of communication. Mobile phones, internet and computers have turned the world into a global village.
Hologram technology (three-dimensional image formation) has brought a revolutionary change in the modern technology.
Simple machines like pulley, lever, inclined plane etc has made the life easy are all inventions of physics.
Electricity, without which life seems impossible, is also an invention of physics.

Q2. What is SI? Name SI base quantities and their units.

Ans: SYSTEM INTERNATIONAL (SI):

The eleventh General Conference on Weight and Measures held in Paris (France) in 1960, adopted a world-wide system of measurements called System International (SI). In this system, seven quantities were chosen as Basic Quantities and their units of were defined and called Base units, from which all other units are derived. The seven basic physical quantities along with their SI base units and symbols are given in table below.

Base Quantity	Unit
Quantity Name	Symbol	Unit Name	Symbol
Length	l	meter	m
Mass	m	kilogram	kg
Time	t	second	s
Electric current	I	ampere	A
Intensity of light/ Luminous intensity	L	candela	cd
Temperature	T	kelvin	K
Amount of substance	N	mole	mol

Q3. What are physical quantities? Distinguish between base and derived physical quantities.

Ans: PHYSICAL QUANTITIES:

All the measurable quantities are called physical quantities.

The quantities which can be measured are known as physical quantities.

EXAMPLES:

Length, mass, time, distance etc are physical quantities.

PHYSICAL QUANTITIES:

Physical quantities are divided into:

Base quantities
Derived quantities

Difference between Base and Derived Quantities:

Base Quantities	Derived Quantities
These are the quantities on the bases of which all other quantities are defined.	These are the quantities which are defined in terms of base quantities.
Base quantities are selected and are only seven in number.	There exist a large number of derived quantities, having no fix number.
Their units are defined and standardized and are called base units.	Their units are obtained by multiplying or dividing one or more base units with each other.
These are the elementary or fundamental quantities and cannot be reduced further.	These quantities can be reduced (simplified)to elementary level i-e in term of base quantities.
Length, mass, time, temperature, electric current, intensity of light and amount of substance are base quantities.	Speed, area, volume, force, work, power etc are some examples of derived units.

Q4. What is standard form or scientific notation?

Ans: SCIENTIFIC NOTATION:

A simple scientific way to write a very large or very small number in term of some power of 10 is called standard form or scientific notation.

EXPLANATION:

In scientific notation, a number is expressed in some power of 10 multiplied by a number between 1 and 9. i-e

N = m x 10n

where “N” represents the very large or small number, “m” represents a number whose first digit is non-zero and is between 0 and 9 and “n” represent the power of 10 which may be positive or negative.

EXAMPLES:

The sun is 150 million km away from the Earth. In scientific notation:

150 million km = 150 x 106 km = 1.50 x 102 x 106 x 103 m = 1.5 x 106+2+3m = 1.5 x 1011 m

Similarly, the diameter of atomic nucleus is about 0.000000000000001m, which is written as 1 x 10-15 m in standard form or scientific notation.

Q5. What are prefixes? Explain with examples.

Ans: PREFIXES:

Prefixes are the words or letters added before SI units to represent their multiples and sub-multiples.

EXPLANATION:

Some of the quantities are either very large or very small. To express such numbers, special names and symbols are assigned to certain power of 10 like centi, kilo, exa etc.

EXAMPLE:

To measure the thickness of a paper, we need a smaller unit like millimeter rather than meter. Similarly to measure the distance between the sun and the earth we use kilometer rather than meter.

A set of useful prefixes is given below.

Prefix	Symbol	Multiplier	Prefix	Symbol	Multiplier
exa	E	1018	deci	d	10-1
peta	P	1015	centi	c	10-2
tera	T	1012	milli	m	10-3
giga	G	109	micro		10-6
mega	M	106	nano	n	10-9
kilo	k	103	pico	p	10-12
hecto	h	102	femto	f	10-15
deca	da	101	atto	a	10-18

Q6. Describe the construction and use for measurement of the following instruments.

Vernier Calipers b. Screw Gauge

Ans: VERNIER CALIPERS:

Vernier calipers was introduced by Pierre Vernier (France) in 1631. It is an instrument used to measure length or diameter etc of small objects accurately.

CONSTRUCTION:

Vernier calipers consists of two jaws.

Fixed jaw with main scale attached to it.
Moveable jaw with vernier scale attached to it.

These movable and fixed jaws have measuring tips for taking internal and external measurements.

MAIN SCALE:

Main scale is in the form of steel bar and has centimeter or millimeter marks on it.

VERNIER SCALE:

Vernier scale slides over main scale and has 10 divisions each of which is 0.9 mm.

LEAST COUNT OF VERNIER CALIPERS:

The smallest length that can be measured by using a vernier calipers is called the least of vernier calipers. It is the difference between the value of one main scale division and the value of one vernier scale division. Least count of vernier calipers is also called vernier constant. It is obtained by dividing “1” main scale division (1 mm) by total numbers of vernier scale divisions which is 10, i-e

L.C = mm = 0.1 mm = 0.01 cm

ZERO ERROR:

If the zero on the vernier scale does not coincide with the zero on the main scale, the vernier calipers said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

When zero of vernier scale lies ahead (or is on the left side) of zero of Maine scale then this is called negative error. It is added to the actual reading for zero correction.

USES OF VERNIER CALIPERS:

Vernier calipers is an instrument used to measure:

Small lengths accurately up to 0.1mm or 0.01 cm.
The thickness, diameter or width of an object
The internal or external diameter of hollow cylinder.

SCREW GAUGE:

Screw gauge was invented by William Gascoigne in the year 1638. The screw gauge is an instrument used for measuring accurately the diameter of a thin wire or the thickness of a sheet of metal.

CONSTRUCTION:

A screw gauge consists of a “U” shaped frame with a metal stud at its one end and a graduated cylinder fitted with other end. A bolt is present at one end of the cylinder. There is a circular scale around the cylinder consisting of 100 divisions.

LEAST COUNT OF SCREW GAUGE:

L.C = mm = 0.01 mm = 0.001 cm

ZERO ERROR:

If the zero on the circular scale does not coincide with the zero on the horizontal line, the screw gauge said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

If zero of circular scale lies ahead of zero of horizontal then it is called negative error. It is added to the actual reading for zero correction.

USES OF SCREW GAUGE:

The screw gauge is used to measure very short lengths such as the thickness of metal sheet or diameter of a wire up to 0.01 mm or 0.001cm.

Q7. What is meant by significant figures of measurements? What are the main points to be kept in mind while determining the significant figures of a measurement?

Ans: SIGNIFICANT FIGURES:

The significant figures are all the digits that are known accurately and the first estimated digit.

Rules for Writing Significant Figures:

Non- zero digits are always significant. For example, there are 3 significant figures in 98.3.
Zeros between two significant figures are also significant. For example, there are 7 significant figures in 97.65003.
Ending zeros on the right in decimal fraction are significant. For example, in 5.700 there are four significant figures.
Zeros on the left side of the decimal are not significant. For example, in 0.000754 there are three significant figures.
In a standard notation, all digits before the power of 10 are significant. For example in 3.71 x109, there are three significant figures in it.
Zeros on the right of the significant figures may or may not be significant. In decimal fractions zero to the right of a decimal fraction are significant. For example, in 9.800 there are four significant figures. For example, in number 80,000 we may have 1, 2 or even 5 significant figures.

NUMERICAL PROBLEMS:

Write the numbers in prefix to power of ten.
Mechanical nano-oscillator can detect a mass change as small as 10-21 kg.
The nearest neutron start is about 3.00 x 1018m away from earth.
Earth to sun distance is 149.6 million kilometer.

Solution:

Given:

Mass of charge = m = 10-21kg

Required:

Prefix to power of ten = ?

Calculations:

Mass of charge = m = 10-21 kg

Since 1 kg = 1000 g = 103 g, therefore,

m = 10-21 x 103 g

m = 10-21+3 g
m = 10-18 g

where 10-18 is represented by atto, therefore

m = 1 atto.g = 1 ag

Given:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Required:

Prefix to power of ten = ?

Calculations:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Since 1018 is represented by exa, therefore,

s = 3.00 exa. m

s = 3 Em
Given:

Distance of sun from earth = s = 149.6 Million km

Required:

Prefix to power of ten = ?

Calculations:

Distance of sun from earth = s = 149.6 Million km

Since 1 million km = 1,000,000 km = 106 km and 1 km = 1000 m = 103 m, therefore

s = 149.6 x 106 x 103 m

s = 149.6 x 106+3 m
s = 149.6 x 109 m

Since 109 is represented by giga, therefore,

s = 149.6 giga. m

s = 149.6 Gm

An angstrom [symbol Ao] is a unit of length (commonly used in physics), defined as 10-10m which is of the order of the diameter of an atom. Find:
How many nanometer are in 1.0 angstrom?
How many femtometers or fermis (the common unit of length in nuclear physics) are in 1.0 angstrom?
How many angstrom are in 1.0 m?

Solution:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Nanometer in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 nm = 1 x 10-9m ⇒ 1m = 109nm therefore,

1 Ao = 10-10m = 10-10 x 109nm

1 Ao = 10-10+9 nm
1 Ao = 10-1 nm
1 Ao = 0.1 nm
Given:

1 angstrom = 1 Ao = 10-10m

Required:

Femtometer or fermis in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 fm = 1 x 10-15m ⇒ 1m = 1015fm therefore,

1 Ao = 10-10m = 10-10 x 1015fm

1 Ao = 10-10+15 fm
1 Ao = 105 fm
Given:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Angstrom in 1.0 m = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

10-10m = 1 Ao
1 m = Ao
1m = 1010 Ao

The speed of light is c = 299,792,458 m/sec.
Write this value in scientific notation.
Express the speed of light to:
Five significant figures.
Three significant figures.

Solution:

Given:

Speed of light = c = 299,792,458 m/sec

Required:

Value in scientific notation = ?

Calculations:

Speed of light = c = 299,792,458 m/s

Since we move 8 decimal places to the left, therefore,

c = 2.99792458 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to five significant figures =?

Calculations:

To express the value to five significant figures, the last four digits before the power of 10 are rounded off and the dropping digit is 2 < 5 so it will be ignored and the last retained digit i-e 9 will remain as it is, therefore,

c = 2.99792458 x 108 m/s = 2.9979 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to three significant figures =?

Calculations:

To express the value to three significant figures, the dropping digit is 7 > 5, so the last retained digit i-e 9 will be increased by 1, therefore

c = 2.99792458 x 108 m/s = 3.00 x 108 m/s

Express the following in terms of power of 10.
7 nanometer (b) 96 megawatt (c) 2 gigabite (d) 43 picofarad

(e) 2 milli meter

Solution:

7 nanometer = 7 x 10-9 m (Since 1 nm = 10-9m)
96 megawatt = 96 x 106 watt (Since 1 megawatt = 106 watt)
96 x 106 watt = 9.6 x 101 x 106 watt
96 x 106 watt = 9.6 x 101+6 watt
96 x 106 watt = 9.6 x 107 watt
2 gegabite = 2 x 109 bite (Since 1 gegabite = 109 bite)
43 picofarad = 43 x 10-12 farad (Since 1 picofarad = 10-12 farad)
43 picofarad = 4.3 x 101x 10-12 farad
43 picofarad = 9.6 x 101-12 farad
43 picofarad = 9.6 x 10-11 farad
2 milli meter = 2 x 10-3 m (Since 1 mm = 10-3m)

Write the following numbers in standard form.
Mass of bacterial cell = 0.000,000,000,005 kg
Diameter of sun = 1,390,000,000 m

Solution:

Given:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Required:

Value in standard form = ?

Calculations:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Standard form = N = m x 10n

We will move 12 decimal places to the right, therefore,

m = 000,000,000,005.0 x 10-12 kg

m = 5 x 10-12kg
Given:

Diameter of sun = D = 1,390,000,000 m

Required:

Value in standard form = ?

Calculations:

Diameter of sun = D = 1,390,000,000 m

Standard form = N = m x 10n

We will move 9 decimal places to the left, therefore,

D = 1.390,000,000 x 109 m

D = 1.39 x 109m

UNIT 1: PHYSICAL QUANTITIES AND MEASUREMENT

EXERCISE:

MULTIPLE CHOICE QUESTIONS:

How many millimeters are there in 10 cm? A. 100 mm
Which of the following quantity can be measured using a micrometer? C. Length
The instrument best measures the internal diameter of pipe is: A. Screw Gauge
Which prefix has the largest value? D. exa
Which of the following is smallest prefix? A. atto
Which of the following numbers shows one significant digit? D. 6 x 102
Which of the following numbers shows 4 significant digits? A. 9.008
A light year is distance travelled by light in one year. It travels about 9.460 x 1015m.

How many significant figures are there in this number? D. 4

0.2 mm in units of meter is: D. Both A and B
KITAB UL MANAZIR is the name of book written by: B. Ibnal Haitham

CONCEPTUAL QUESTIONS:

Give a brief response to the following questions.

Q1. How technology is shaped by physics?

Physics explains “How electrons are emitted from cathode ray tube?” and technology utilizes its answer to make TV tubes.
The principle of reflection and detection of electromagnetic waves led towards the invention of Radar.
The principles of electromagnetic induction are used by the electric power used to generate at power stations.
The automobile technology is based on the principles of thermodynamics.
Solid state physics is the bases of all electronic devices.

Q2. Physics and biology are considered different branches of science. How physics links with biology?

Gravity, a concept explained by physics, affects flow of blood in the body (biology).
Dolphins, bats, and whales use UV-radiations for their movement.
MRI (Magnetic Resonance Imaging) of brain, x-rays of bones, ultrasounds etc are the applications of physics (magnetism and waves).
Plants movements like phototropic, geotropic etc are due to the effects of light and gravity etc, explained by physics.
Greenhouse effect, an invention of physics, is applied for the growth of plants.

Q3. Why are measurements important?

Ans: Measurements help us to better understand the world around us. Measurements help us in several ways by providing a standard for everyday life and processes. . For example:

We need measurements to calculate blood pressure, heart-beat rate.
Proper construction of buildings is due to the proper measurements.
Purchasing and selling of different stuffs are also possible because of measurements.
Weight, temperature, length and even time, concepts we use in everyday life, are all measurements.
Money or currency used in daily life is also measurement.

Q4. Why area is a derived physical quantity?

Ans. Area is a derived physical quantity because it is the product of base physical quantities length and breadth i-e

Area = Length x Breadth

= m x m

= m2

Q5. Name any four derived units and write them as their base units.

Ans. Derived Units; The units which are expressed in terms of base units are known as derived units.

Physical Quantities	SI Units	In terms of base units
Force	newton (kg. m/s2)	kg. m/s . s
Energy	joule (Nm)	kg.m. m/s . s
Acceleration	m/s2	m/s.s
Momentum	kg. m/s	kg. m/s

Q6. Why in physics, we need to write in scientific notation?

Q7. What is least count? How least count for vernier caliper and screw gauge are defined?

Ans: Least Count:

The smallest accurate value that can be measured by a measuring instrument is called least count of that instrument. For example the least count of a wall clock is one second.

Least Count of Vernier Caliper:

L.C = mm = 0.1 mm = 0.01 cm

Least Count of Screw Gauge:

L.C = mm = 0.01 mm = 0.001 cm

Q8. How can we find the volume of a small pebble with the help of measuring cylinder?

Ans: Following are the steps taken to measure the volume of a small pebble with the help of measuring cylinder.

Take a measuring cylinder and pour some water in it.
Record the reading and note it as V1, it gives the volume of water.
Put a pebble of unknown volume into water. Note that water level rises up.
Record the reading again and note it as V2, it gives the volume of both the water and the pebble.
The difference between both the readings () gives the volume of pebble. i-e

Volume of pebble = = V2 – V1

COMPREHENSIVE QUESTIONS

Give an extended response to the following questions.

Q1. Define physics. How physics play a crucial role in science, technology and society.

Ans. PHYSICS:

Physics is the branch of science that deals with the study of properties of physical universe i-e energy and matter, and the mutual relation between them.

EXPLANATION:

ROLE OF PHYSICS IN SCIENCE:

ROLE OF PHYSICS IN TECHNOLOGY:

ROLE OF PHYSICS IN SOCIETY:

Physics provides basic understanding for developing new medical instruments and technologies such as x-ray, ultrasound, CT scan, MRI and laser technology.
The study of physics in information technology has improved the standard of communication. Mobile phones, internet and computers have turned the world into a global village.
Hologram technology (three-dimensional image formation) has brought a revolutionary change in the modern technology.
Simple machines like pulley, lever, inclined plane etc has made the life easy are all inventions of physics.
Electricity, without which life seems impossible, is also an invention of physics.

Q2. What is SI? Name SI base quantities and their units.

Ans: SYSTEM INTERNATIONAL (SI):

Base Quantity	Unit
Quantity Name	Symbol	Unit Name	Symbol
Length	l	meter	m
Mass	m	kilogram	kg
Time	t	second	s
Electric current	I	ampere	A
Intensity of light/ Luminous intensity	L	candela	cd
Temperature	T	kelvin	K
Amount of substance	N	mole	mol

Q3. What are physical quantities? Distinguish between base and derived physical quantities.

Ans: PHYSICAL QUANTITIES:

All the measurable quantities are called physical quantities.

The quantities which can be measured are known as physical quantities.

EXAMPLES:

Length, mass, time, distance etc are physical quantities.

PHYSICAL QUANTITIES:

Physical quantities are divided into:

Base quantities
Derived quantities

Difference between Base and Derived Quantities:

Base Quantities	Derived Quantities
These are the quantities on the bases of which all other quantities are defined.	These are the quantities which are defined in terms of base quantities.
Base quantities are selected and are only seven in number.	There exist a large number of derived quantities, having no fix number.
Their units are defined and standardized and are called base units.	Their units are obtained by multiplying or dividing one or more base units with each other.
These are the elementary or fundamental quantities and cannot be reduced further.	These quantities can be reduced (simplified)to elementary level i-e in term of base quantities.
Length, mass, time, temperature, electric current, intensity of light and amount of substance are base quantities.	Speed, area, volume, force, work, power etc are some examples of derived units.

Q4. What is standard form or scientific notation?

Ans: SCIENTIFIC NOTATION:

A simple scientific way to write a very large or very small number in term of some power of 10 is called standard form or scientific notation.

EXPLANATION:

In scientific notation, a number is expressed in some power of 10 multiplied by a number between 1 and 9. i-e

N = m x 10n

EXAMPLES:

The sun is 150 million km away from the Earth. In scientific notation:

150 million km = 150 x 106 km = 1.50 x 102 x 106 x 103 m = 1.5 x 106+2+3m = 1.5 x 1011 m

Similarly, the diameter of atomic nucleus is about 0.000000000000001m, which is written as 1 x 10-15 m in standard form or scientific notation.

Q5. What are prefixes? Explain with examples.

Ans: PREFIXES:

Prefixes are the words or letters added before SI units to represent their multiples and sub-multiples.

EXPLANATION:

Some of the quantities are either very large or very small. To express such numbers, special names and symbols are assigned to certain power of 10 like centi, kilo, exa etc.

EXAMPLE:

To measure the thickness of a paper, we need a smaller unit like millimeter rather than meter. Similarly to measure the distance between the sun and the earth we use kilometer rather than meter.

A set of useful prefixes is given below.

Prefix	Symbol	Multiplier	Prefix	Symbol	Multiplier
exa	E	1018	deci	d	10-1
peta	P	1015	centi	c	10-2
tera	T	1012	milli	m	10-3
giga	G	109	micro		10-6
mega	M	106	nano	n	10-9
kilo	k	103	pico	p	10-12
hecto	h	102	femto	f	10-15
deca	da	101	atto	a	10-18

Q6. Describe the construction and use for measurement of the following instruments.

Vernier Calipers b. Screw Gauge

Ans: VERNIER CALIPERS:

Vernier calipers was introduced by Pierre Vernier (France) in 1631. It is an instrument used to measure length or diameter etc of small objects accurately.

CONSTRUCTION:

Vernier calipers consists of two jaws.

Fixed jaw with main scale attached to it.
Moveable jaw with vernier scale attached to it.

These movable and fixed jaws have measuring tips for taking internal and external measurements.

MAIN SCALE:

Main scale is in the form of steel bar and has centimeter or millimeter marks on it.

VERNIER SCALE:

Vernier scale slides over main scale and has 10 divisions each of which is 0.9 mm.

LEAST COUNT OF VERNIER CALIPERS:

L.C = mm = 0.1 mm = 0.01 cm

ZERO ERROR:

If the zero on the vernier scale does not coincide with the zero on the main scale, the vernier calipers said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

When zero of vernier scale lies ahead (or is on the left side) of zero of Maine scale then this is called negative error. It is added to the actual reading for zero correction.

USES OF VERNIER CALIPERS:

Vernier calipers is an instrument used to measure:

Small lengths accurately up to 0.1mm or 0.01 cm.
The thickness, diameter or width of an object
The internal or external diameter of hollow cylinder.

SCREW GAUGE:

Screw gauge was invented by William Gascoigne in the year 1638. The screw gauge is an instrument used for measuring accurately the diameter of a thin wire or the thickness of a sheet of metal.

CONSTRUCTION:

LEAST COUNT OF SCREW GAUGE:

L.C = mm = 0.01 mm = 0.001 cm

ZERO ERROR:

If the zero on the circular scale does not coincide with the zero on the horizontal line, the screw gauge said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

If zero of circular scale lies ahead of zero of horizontal then it is called negative error. It is added to the actual reading for zero correction.

USES OF SCREW GAUGE:

The screw gauge is used to measure very short lengths such as the thickness of metal sheet or diameter of a wire up to 0.01 mm or 0.001cm.

Q7. What is meant by significant figures of measurements? What are the main points to be kept in mind while determining the significant figures of a measurement?

Ans: SIGNIFICANT FIGURES:

The significant figures are all the digits that are known accurately and the first estimated digit.

Rules for Writing Significant Figures:

Non- zero digits are always significant. For example, there are 3 significant figures in 98.3.
Zeros between two significant figures are also significant. For example, there are 7 significant figures in 97.65003.
Ending zeros on the right in decimal fraction are significant. For example, in 5.700 there are four significant figures.
Zeros on the left side of the decimal are not significant. For example, in 0.000754 there are three significant figures.
In a standard notation, all digits before the power of 10 are significant. For example in 3.71 x109, there are three significant figures in it.
Zeros on the right of the significant figures may or may not be significant. In decimal fractions zero to the right of a decimal fraction are significant. For example, in 9.800 there are four significant figures. For example, in number 80,000 we may have 1, 2 or even 5 significant figures.

NUMERICAL PROBLEMS:

Write the numbers in prefix to power of ten.
Mechanical nano-oscillator can detect a mass change as small as 10-21 kg.
The nearest neutron start is about 3.00 x 1018m away from earth.
Earth to sun distance is 149.6 million kilometer.

Solution:

Given:

Mass of charge = m = 10-21kg

Required:

Prefix to power of ten = ?

Calculations:

Mass of charge = m = 10-21 kg

Since 1 kg = 1000 g = 103 g, therefore,

m = 10-21 x 103 g

m = 10-21+3 g
m = 10-18 g

where 10-18 is represented by atto, therefore

m = 1 atto.g = 1 ag

Given:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Required:

Prefix to power of ten = ?

Calculations:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Since 1018 is represented by exa, therefore,

s = 3.00 exa. m

s = 3 Em
Given:

Distance of sun from earth = s = 149.6 Million km

Required:

Prefix to power of ten = ?

Calculations:

Distance of sun from earth = s = 149.6 Million km

Since 1 million km = 1,000,000 km = 106 km and 1 km = 1000 m = 103 m, therefore

s = 149.6 x 106 x 103 m

s = 149.6 x 106+3 m
s = 149.6 x 109 m

Since 109 is represented by giga, therefore,

s = 149.6 giga. m

s = 149.6 Gm

An angstrom [symbol Ao] is a unit of length (commonly used in physics), defined as 10-10m which is of the order of the diameter of an atom. Find:
How many nanometer are in 1.0 angstrom?
How many femtometers or fermis (the common unit of length in nuclear physics) are in 1.0 angstrom?
How many angstrom are in 1.0 m?

Solution:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Nanometer in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 nm = 1 x 10-9m ⇒ 1m = 109nm therefore,

1 Ao = 10-10m = 10-10 x 109nm

1 Ao = 10-10+9 nm
1 Ao = 10-1 nm
1 Ao = 0.1 nm
Given:

1 angstrom = 1 Ao = 10-10m

Required:

Femtometer or fermis in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 fm = 1 x 10-15m ⇒ 1m = 1015fm therefore,

1 Ao = 10-10m = 10-10 x 1015fm

1 Ao = 10-10+15 fm
1 Ao = 105 fm
Given:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Angstrom in 1.0 m = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

10-10m = 1 Ao
1 m = Ao
1m = 1010 Ao

The speed of light is c = 299,792,458 m/sec.
Write this value in scientific notation.
Express the speed of light to:
Five significant figures.
Three significant figures.

Solution:

Given:

Speed of light = c = 299,792,458 m/sec

Required:

Value in scientific notation = ?

Calculations:

Speed of light = c = 299,792,458 m/s

Since we move 8 decimal places to the left, therefore,

c = 2.99792458 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to five significant figures =?

Calculations:

c = 2.99792458 x 108 m/s = 2.9979 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to three significant figures =?

Calculations:

To express the value to three significant figures, the dropping digit is 7 > 5, so the last retained digit i-e 9 will be increased by 1, therefore

c = 2.99792458 x 108 m/s = 3.00 x 108 m/s

Express the following in terms of power of 10.
7 nanometer (b) 96 megawatt (c) 2 gigabite (d) 43 picofarad

(e) 2 milli meter

Solution:

7 nanometer = 7 x 10-9 m (Since 1 nm = 10-9m)
96 megawatt = 96 x 106 watt (Since 1 megawatt = 106 watt)
96 x 106 watt = 9.6 x 101 x 106 watt
96 x 106 watt = 9.6 x 101+6 watt
96 x 106 watt = 9.6 x 107 watt
2 gegabite = 2 x 109 bite (Since 1 gegabite = 109 bite)
43 picofarad = 43 x 10-12 farad (Since 1 picofarad = 10-12 farad)
43 picofarad = 4.3 x 101x 10-12 farad
43 picofarad = 9.6 x 101-12 farad
43 picofarad = 9.6 x 10-11 farad
2 milli meter = 2 x 10-3 m (Since 1 mm = 10-3m)

Write the following numbers in standard form.
Mass of bacterial cell = 0.000,000,000,005 kg
Diameter of sun = 1,390,000,000 m

Solution:

Given:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Required:

Value in standard form = ?

Calculations:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Standard form = N = m x 10n

We will move 12 decimal places to the right, therefore,

m = 000,000,000,005.0 x 10-12 kg

m = 5 x 10-12kg
Given:

Diameter of sun =

Chapter No 1 Physics Notes For Class 9th

UNIT 1: PHYSICAL QUANTITIES AND MEASUREMENT

EXERCISE:

MULTIPLE CHOICE QUESTIONS:

How many millimeters are there in 10 cm? A. 100 mm
Which of the following quantity can be measured using a micrometer? C. Length
The instrument best measures the internal diameter of pipe is: A. Screw Gauge
Which prefix has the largest value? D. exa
Which of the following is smallest prefix? A. atto
Which of the following numbers shows one significant digit? D. 6 x 102
Which of the following numbers shows 4 significant digits? A. 9.008
A light year is distance travelled by light in one year. It travels about 9.460 x 1015m.

How many significant figures are there in this number? D. 4

0.2 mm in units of meter is: D. Both A and B
KITAB UL MANAZIR is the name of book written by: B. Ibnal Haitham

CONCEPTUAL QUESTIONS:

Give a brief response to the following questions.

Q1. How technology is shaped by physics?

Physics explains “How electrons are emitted from cathode ray tube?” and technology utilizes its answer to make TV tubes.
The principle of reflection and detection of electromagnetic waves led towards the invention of Radar.
The principles of electromagnetic induction are used by the electric power used to generate at power stations.
The automobile technology is based on the principles of thermodynamics.
Solid state physics is the bases of all electronic devices.

Q2. Physics and biology are considered different branches of science. How physics links with biology?

Gravity, a concept explained by physics, affects flow of blood in the body (biology).
Dolphins, bats, and whales use UV-radiations for their movement.
MRI (Magnetic Resonance Imaging) of brain, x-rays of bones, ultrasounds etc are the applications of physics (magnetism and waves).
Plants movements like phototropic, geotropic etc are due to the effects of light and gravity etc, explained by physics.
Greenhouse effect, an invention of physics, is applied for the growth of plants.

Q3. Why are measurements important?

Ans: Measurements help us to better understand the world around us. Measurements help us in several ways by providing a standard for everyday life and processes. . For example:

We need measurements to calculate blood pressure, heart-beat rate.
Proper construction of buildings is due to the proper measurements.
Purchasing and selling of different stuffs are also possible because of measurements.
Weight, temperature, length and even time, concepts we use in everyday life, are all measurements.
Money or currency used in daily life is also measurement.

Q4. Why area is a derived physical quantity?

Ans. Area is a derived physical quantity because it is the product of base physical quantities length and breadth i-e

Area = Length x Breadth

= m x m

= m2

Q5. Name any four derived units and write them as their base units.

Ans. Derived Units; The units which are expressed in terms of base units are known as derived units.

Physical Quantities	SI Units	In terms of base units
Force	newton (kg. m/s2)	kg. m/s . s
Energy	joule (Nm)	kg.m. m/s . s
Acceleration	m/s2	m/s.s
Momentum	kg. m/s	kg. m/s

Q6. Why in physics, we need to write in scientific notation?

Q7. What is least count? How least count for vernier caliper and screw gauge are defined?

Ans: Least Count:

The smallest accurate value that can be measured by a measuring instrument is called least count of that instrument. For example the least count of a wall clock is one second.

Least Count of Vernier Caliper:

L.C = mm = 0.1 mm = 0.01 cm

Least Count of Screw Gauge:

L.C = mm = 0.01 mm = 0.001 cm

Q8. How can we find the volume of a small pebble with the help of measuring cylinder?

Ans: Following are the steps taken to measure the volume of a small pebble with the help of measuring cylinder.

Take a measuring cylinder and pour some water in it.
Record the reading and note it as V1, it gives the volume of water.
Put a pebble of unknown volume into water. Note that water level rises up.
Record the reading again and note it as V2, it gives the volume of both the water and the pebble.
The difference between both the readings () gives the volume of pebble. i-e

Volume of pebble = = V2 – V1

COMPREHENSIVE QUESTIONS

Give an extended response to the following questions.

Q1. Define physics. How physics play a crucial role in science, technology and society.

Ans. PHYSICS:

Physics is the branch of science that deals with the study of properties of physical universe i-e energy and matter, and the mutual relation between them.

EXPLANATION:

ROLE OF PHYSICS IN SCIENCE:

ROLE OF PHYSICS IN TECHNOLOGY:

ROLE OF PHYSICS IN SOCIETY:

Physics provides basic understanding for developing new medical instruments and technologies such as x-ray, ultrasound, CT scan, MRI and laser technology.
The study of physics in information technology has improved the standard of communication. Mobile phones, internet and computers have turned the world into a global village.
Hologram technology (three-dimensional image formation) has brought a revolutionary change in the modern technology.
Simple machines like pulley, lever, inclined plane etc has made the life easy are all inventions of physics.
Electricity, without which life seems impossible, is also an invention of physics.

Q2. What is SI? Name SI base quantities and their units.

Ans: SYSTEM INTERNATIONAL (SI):

Base Quantity	Unit
Quantity Name	Symbol	Unit Name	Symbol
Length	l	meter	m
Mass	m	kilogram	kg
Time	t	second	s
Electric current	I	ampere	A
Intensity of light/ Luminous intensity	L	candela	cd
Temperature	T	kelvin	K
Amount of substance	N	mole	mol

Q3. What are physical quantities? Distinguish between base and derived physical quantities.

Ans: PHYSICAL QUANTITIES:

All the measurable quantities are called physical quantities.

The quantities which can be measured are known as physical quantities.

EXAMPLES:

Length, mass, time, distance etc are physical quantities.

PHYSICAL QUANTITIES:

Physical quantities are divided into:

Base quantities
Derived quantities

Difference between Base and Derived Quantities:

Base Quantities	Derived Quantities
These are the quantities on the bases of which all other quantities are defined.	These are the quantities which are defined in terms of base quantities.
Base quantities are selected and are only seven in number.	There exist a large number of derived quantities, having no fix number.
Their units are defined and standardized and are called base units.	Their units are obtained by multiplying or dividing one or more base units with each other.
These are the elementary or fundamental quantities and cannot be reduced further.	These quantities can be reduced (simplified)to elementary level i-e in term of base quantities.
Length, mass, time, temperature, electric current, intensity of light and amount of substance are base quantities.	Speed, area, volume, force, work, power etc are some examples of derived units.

Q4. What is standard form or scientific notation?

Ans: SCIENTIFIC NOTATION:

A simple scientific way to write a very large or very small number in term of some power of 10 is called standard form or scientific notation.

EXPLANATION:

In scientific notation, a number is expressed in some power of 10 multiplied by a number between 1 and 9. i-e

N = m x 10n

EXAMPLES:

The sun is 150 million km away from the Earth. In scientific notation:

150 million km = 150 x 106 km = 1.50 x 102 x 106 x 103 m = 1.5 x 106+2+3m = 1.5 x 1011 m

Similarly, the diameter of atomic nucleus is about 0.000000000000001m, which is written as 1 x 10-15 m in standard form or scientific notation.

Q5. What are prefixes? Explain with examples.

Ans: PREFIXES:

Prefixes are the words or letters added before SI units to represent their multiples and sub-multiples.

EXPLANATION:

Some of the quantities are either very large or very small. To express such numbers, special names and symbols are assigned to certain power of 10 like centi, kilo, exa etc.

EXAMPLE:

To measure the thickness of a paper, we need a smaller unit like millimeter rather than meter. Similarly to measure the distance between the sun and the earth we use kilometer rather than meter.

A set of useful prefixes is given below.

Prefix	Symbol	Multiplier	Prefix	Symbol	Multiplier
exa	E	1018	deci	d	10-1
peta	P	1015	centi	c	10-2
tera	T	1012	milli	m	10-3
giga	G	109	micro		10-6
mega	M	106	nano	n	10-9
kilo	k	103	pico	p	10-12
hecto	h	102	femto	f	10-15
deca	da	101	atto	a	10-18

Q6. Describe the construction and use for measurement of the following instruments.

Vernier Calipers b. Screw Gauge

Ans: VERNIER CALIPERS:

Vernier calipers was introduced by Pierre Vernier (France) in 1631. It is an instrument used to measure length or diameter etc of small objects accurately.

CONSTRUCTION:

Vernier calipers consists of two jaws.

Fixed jaw with main scale attached to it.
Moveable jaw with vernier scale attached to it.

These movable and fixed jaws have measuring tips for taking internal and external measurements.

MAIN SCALE:

Main scale is in the form of steel bar and has centimeter or millimeter marks on it.

VERNIER SCALE:

Vernier scale slides over main scale and has 10 divisions each of which is 0.9 mm.

LEAST COUNT OF VERNIER CALIPERS:

L.C = mm = 0.1 mm = 0.01 cm

ZERO ERROR:

If the zero on the vernier scale does not coincide with the zero on the main scale, the vernier calipers said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

When zero of vernier scale lies ahead (or is on the left side) of zero of Maine scale then this is called negative error. It is added to the actual reading for zero correction.

USES OF VERNIER CALIPERS:

Vernier calipers is an instrument used to measure:

Small lengths accurately up to 0.1mm or 0.01 cm.
The thickness, diameter or width of an object
The internal or external diameter of hollow cylinder.

SCREW GAUGE:

Screw gauge was invented by William Gascoigne in the year 1638. The screw gauge is an instrument used for measuring accurately the diameter of a thin wire or the thickness of a sheet of metal.

CONSTRUCTION:

LEAST COUNT OF SCREW GAUGE:

L.C = mm = 0.01 mm = 0.001 cm

ZERO ERROR:

If the zero on the circular scale does not coincide with the zero on the horizontal line, the screw gauge said to has zero error. Zero error may be positive or negative.

POSITIVE ZERO ERROR:

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

NEGATIVE ZERO ERROR:

If zero of circular scale lies ahead of zero of horizontal then it is called negative error. It is added to the actual reading for zero correction.

USES OF SCREW GAUGE:

The screw gauge is used to measure very short lengths such as the thickness of metal sheet or diameter of a wire up to 0.01 mm or 0.001cm.

Q7. What is meant by significant figures of measurements? What are the main points to be kept in mind while determining the significant figures of a measurement?

Ans: SIGNIFICANT FIGURES:

The significant figures are all the digits that are known accurately and the first estimated digit.

Rules for Writing Significant Figures:

Non- zero digits are always significant. For example, there are 3 significant figures in 98.3.
Zeros between two significant figures are also significant. For example, there are 7 significant figures in 97.65003.
Ending zeros on the right in decimal fraction are significant. For example, in 5.700 there are four significant figures.
Zeros on the left side of the decimal are not significant. For example, in 0.000754 there are three significant figures.
In a standard notation, all digits before the power of 10 are significant. For example in 3.71 x109, there are three significant figures in it.
Zeros on the right of the significant figures may or may not be significant. In decimal fractions zero to the right of a decimal fraction are significant. For example, in 9.800 there are four significant figures. For example, in number 80,000 we may have 1, 2 or even 5 significant figures.

NUMERICAL PROBLEMS:

Write the numbers in prefix to power of ten.
Mechanical nano-oscillator can detect a mass change as small as 10-21 kg.
The nearest neutron start is about 3.00 x 1018m away from earth.
Earth to sun distance is 149.6 million kilometer.

Solution:

Given:

Mass of charge = m = 10-21kg

Required:

Prefix to power of ten = ?

Calculations:

Mass of charge = m = 10-21 kg

Since 1 kg = 1000 g = 103 g, therefore,

m = 10-21 x 103 g

m = 10-21+3 g
m = 10-18 g

where 10-18 is represented by atto, therefore

m = 1 atto.g = 1 ag

Given:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Required:

Prefix to power of ten = ?

Calculations:

Distance of nearest neutron star from earth = s = 3.00 x 1018m

Since 1018 is represented by exa, therefore,

s = 3.00 exa. m

s = 3 Em
Given:

Distance of sun from earth = s = 149.6 Million km

Required:

Prefix to power of ten = ?

Calculations:

Distance of sun from earth = s = 149.6 Million km

Since 1 million km = 1,000,000 km = 106 km and 1 km = 1000 m = 103 m, therefore

s = 149.6 x 106 x 103 m

s = 149.6 x 106+3 m
s = 149.6 x 109 m

Since 109 is represented by giga, therefore,

s = 149.6 giga. m

s = 149.6 Gm

An angstrom [symbol Ao] is a unit of length (commonly used in physics), defined as 10-10m which is of the order of the diameter of an atom. Find:
How many nanometer are in 1.0 angstrom?
How many femtometers or fermis (the common unit of length in nuclear physics) are in 1.0 angstrom?
How many angstrom are in 1.0 m?

Solution:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Nanometer in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 nm = 1 x 10-9m ⇒ 1m = 109nm therefore,

1 Ao = 10-10m = 10-10 x 109nm

1 Ao = 10-10+9 nm
1 Ao = 10-1 nm
1 Ao = 0.1 nm
Given:

1 angstrom = 1 Ao = 10-10m

Required:

Femtometer or fermis in 1.0 Ao = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

Since 1 fm = 1 x 10-15m ⇒ 1m = 1015fm therefore,

1 Ao = 10-10m = 10-10 x 1015fm

1 Ao = 10-10+15 fm
1 Ao = 105 fm
Given:

Given:

1 angstrom = 1 Ao = 10-10m

Required:

Angstrom in 1.0 m = ?

Calculations:

1 angstrom = 1 Ao = 10-10m

10-10m = 1 Ao
1 m = Ao
1m = 1010 Ao

The speed of light is c = 299,792,458 m/sec.
Write this value in scientific notation.
Express the speed of light to:
Five significant figures.
Three significant figures.

Solution:

Given:

Speed of light = c = 299,792,458 m/sec

Required:

Value in scientific notation = ?

Calculations:

Speed of light = c = 299,792,458 m/s

Since we move 8 decimal places to the left, therefore,

c = 2.99792458 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to five significant figures =?

Calculations:

c = 2.99792458 x 108 m/s = 2.9979 x 108 m/s

Given:

c = 2.99792458 x 108 m/s

Required:

Value of c to three significant figures =?

Calculations:

To express the value to three significant figures, the dropping digit is 7 > 5, so the last retained digit i-e 9 will be increased by 1, therefore

c = 2.99792458 x 108 m/s = 3.00 x 108 m/s

Express the following in terms of power of 10.
7 nanometer (b) 96 megawatt (c) 2 gigabite (d) 43 picofarad

(e) 2 milli meter

Solution:

7 nanometer = 7 x 10-9 m (Since 1 nm = 10-9m)
96 megawatt = 96 x 106 watt (Since 1 megawatt = 106 watt)
96 x 106 watt = 9.6 x 101 x 106 watt
96 x 106 watt = 9.6 x 101+6 watt
96 x 106 watt = 9.6 x 107 watt
2 gegabite = 2 x 109 bite (Since 1 gegabite = 109 bite)
43 picofarad = 43 x 10-12 farad (Since 1 picofarad = 10-12 farad)
43 picofarad = 4.3 x 101x 10-12 farad
43 picofarad = 9.6 x 101-12 farad
43 picofarad = 9.6 x 10-11 farad
2 milli meter = 2 x 10-3 m (Since 1 mm = 10-3m)

Write the following numbers in standard form.
Mass of bacterial cell = 0.000,000,000,005 kg
Diameter of sun = 1,390,000,000 m

Solution:

Given:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Required:

Value in standard form = ?

Calculations:

Mass of bacterial cell = m = 0.000,000,000,005 kg

Standard form = N = m x 10n

We will move 12 decimal places to the right, therefore,

m = 000,000,000,005.0 x 10-12 kg

m = 5 x 10-12kg
Given:

Diameter of sun = D = 1,390,000,000 m

Required:

Value in standard form = ?

Calculations:

Diameter of sun = D = 1,390,000,000 m

Standard form = N = m x 10n

We will move 9 decimal places to the left, therefore,

D = 1.390,000,000 x 109 m

D = 1.39 x 109m

D = 1,390,000,000 m

Required:

Value in standard form = ?

Calculations:

Diameter of sun = D = 1,390,000,000 m

Standard form = N = m x 10n

We will move 9 decimal places to the left, therefore,

D = 1.390,000,000 x 109 m

D = 1.39 x 109m

phyicshubPK

Subscribe Us

Chapter No 1 Physics Notes For Class 9th

Chapter No 1 Physics Notes For Class 9th

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

UNIT 1: PHYSICAL QUANTITIES AND MEASUREMENT

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

Chapter No 1 Physics Notes For Class 9th

When zero of vernier scale lies behind (or is on the right of) zero of main scale then it is called positive zero error. It is subtracted from the actual reading for zero correction.

If zero of circular scale lies behind the zero of horizontal line then it is called positive zero error. It is subtracted from the actual reading for zero correction.

Post a Comment

Top Post Ad

Below Post Ad

Ads Area

Report Abuse

Search This Blog

Labels

Contact Form

Popular Posts

Categories

Ad Space

Most Popular

About Us

Footer Copyright

Contact form