physical quantities and measurement · step 3: take the thimble reading with the index line of the...

UNIT 1 (PHYSICAL QUANTITIES AND MEASUREMENT) PHYSICS – IX

Prepared by: Ms. Maimoona Altaf

Physical Quantities and Measurement

1.1 Introduction to Physics

Science: The knowledge gained through observations and experimentations is called

Science. The word science is derived from the Latin word scientia, which means

knowledge.

What is Physics?

Physics is the study of our natural world – from the very large (e.g. the solar system) to the

very small (e.g. the atom). Physics is the most fundamental of all the branches. In physics, we

study matter, energy and their interaction. The laws and principles of Physics help us to

understand nature.

Branches of Physics: The main branches of Physics are given below:

Mechanics: It is the study of motion of objects, its causes and effects.

Heat: It deals with the nature of heat, modes of transfer and effects of heat.

Sound: It deals with the physical aspects of sound waves, their production,

properties and applications.

Light (Optics): It is the study of physical aspects of light, its properties, working and

use of optical instruments.

Electricity and Magnetism: It is the study of the charges at rest and in motion, their

effects and their relationship with magnetism.

Atomic Physics: It is the study of the structure and properties of atoms.

Nuclear Physics: It deals with the properties and behavior of nuclei and the

particles within the nuclei.

Plasma Physics: It is the study of production, properties of the ionic state of matter

– the fourth state of matter.

Geophysics: It is the study of the internal structure of the Earth.

Why do we study Physics?

Physics is key to understanding the world around us, the world inside us, and the world

beyond us. It is the most basic and fundamental science. Physics comprises the study of the

universe from the largest galaxies to the smallest subatomic particles. Moreover, it’s the basis

of many other sciences, including chemistry, oceanography, seismology and astronomy.

Natural Philosophy - Until 18th century

Physical sciences – which deal with the

study of non-living things.

Biological sciences – which are concerned

with the study of living things.

Physics Chemistry Meteorology Geology Astronomy

In 19th century, physical sciences were

divided into five sub-branches.



1.2 & 1.3 Physical Quantities & International System of Units

When you make a measurement, you might get a result like the one above: a distance of 10 m.

The complete measurement is called a physical quantity or in other words all measureable

quantities are known as physical quantities. It is made up of two parts: a number and a unit.

SI units:

The eleventh General Conference on Weight and Measures held in Paris in 1960 adopted a

world-wide system of measurements called International System of Units. The International

System of Units is commonly referred as SI. SI units are the units of measurement in the

widely used international system of units.

Why do we need SI units?

In the past, people used parts of their bodies and things around them as units of

measurement. That was how measuring terms as the foot, yard and horsepower came about.

Unfortunately, such methods of measurement created much confusion because the

measurement varied from individual to individual. It was not until 1968 that scientists agreed

to adopt one universal set of units – the SI units.

Base Quantities:

There are altogether seven physical quantities which form the foundation for other physical

quantities. These physical quantities are called base quantities.

The units that describe base quantities are called base units. Each base quantity has its SI unit.

Base quantity SI unit

Name Symbol Name Symbol

Length l metre m

Mass m kilogram kg

Time t second s

Electric current I ampere A

Intensity of light L candela cd

Temperature T kelvin K

Amount of substance n mole mol



Derived Quantities:

Other common physical quantities such as area, volume, speed, power, etc. are derived from

these seven base quantities. Those physical quantities which are expressed in terms of base

quantities are called derived quantities.

The units used to measure derived quantities are called derived units. Derived units are

defined in terms of base units and are obtained by multiplying or dividing one or more base

units with each other. The unit of area (metre)2 and the unit of volume (metre)3 are based on

the unit of length, which is metre.

Derived quantity SI Unit

Name Symbol Name Symbol

Speed v metre per second ms-1

Acceleration A metre per second per second ms-2

Volume V cubic metre m3

Force F newton N or kgms-2

Pressure P pascal Pa or Nm-2

Density Ρ kilogram per cubic metre Kgm-3

Charge Q coulomb C or As

1.4 Prefixes

Using decimal notation, the distance between air molecules can be expressed as 0.000 000

01m. If we need to mention this number of times, it would be difficult to use this type of

notation. Instead of using decimal notation, it is more convenient to use prefixes to present

the quantity. You can make a unit bigger or smaller by putting an extra symbol, called a prefix,

in front. SI units have the advantage that their multiples and sub-multiples can be expressed in

terms of prefixes.



1.5 Scientific Notation

Another convenient and acceptable way of expressing physical quantities is to us the scientific

notation (standard form). Scientific notation is a way of writing numbers, in which one integer

(1 to 9) is multiplied by an appropriate power of 10. For example, 0.00567 and 16800

expressed in standard form will be 5.67 × 10-3 and 1.68 × 104, respectively.

1.6 Measuring Instruments

Measurement of Lengths:

In Physics, length is an important quantity that is often used. For example, we measure length

to find out how far an object has moved, how much space an object occupies (i.e. the object’s

volume) and how far apart two objects are.

The SI unit for length is metre (m). There is a wide range of lengths in this world. It is

necessary to use appropriate instruments and method to measure different types of length.

The Metre Rule and Measuring Tape:

The metre rule and tape measure are instruments that are commonly used to measure length.

A metre rule can measure lengths of up to one metre. A steel tape measure is suitable for

measuring straight distances longer than a metre, while a cloth tape measure is suitable for

measuring the length along a curved surface, such as a person’s waist.

What is the precision of an instrument?

The smallest unit an instrument can measure is known as precision. The smallest unit on a

metre rule is 0.1 cm or 1 mm. Therefore, the precision/least count of a metre rule is 1 mm.

The thickness of a piece of paper is less than the precision of a metre rule (i.e. 1 mm).

Therefore, you cannot measure the paper’s thickness using a metre rule. You will have to

estimate its thickness.

How do we avoid errors of measurement?

While measuring length, or distance, using a metre rule, eyes should be positioned vertically

above the reading point such that line of sight is perpendicular to the rule. Measurement

errors introduced when eye is positioned either left or right to the reading point.

Note that some metre rules have their zero marks at the very end of the rule. Wear and tear

of the metre rule may make this mark unsuitable for measuring purposes. This worn end may

introduce errors into the readings. Hence, it is better to measure from another point and

subtract it from the final reading. Taking several readings and calculating average also

minimizes errors.



Vernier Callipers:

A pair of Vernier Callipers has a main scale and a sliding vernier scale. It is a useful tool for

measuring both the internal and external diameters of objects. Vernier Callipers are able to

measure to a precision of 0.01 cm.

A vernier callipers consists of two jaws. One is a fixed jaw with main scale attached to it. Main

scale has centimeter and millimeter marks on it. The other jaw is a moveable jaw. It has

vernier scale having 10 divisions. The difference between one small division on main scale

division and one vernier scale division is 0.1 mm. It is called least count (LC) of the Vernier

Callipers. Least count of the Vernier Callipers can also be found as given below:

Inside jaws are used to measure the internal diameter of an object, outside jaws are used to

measure the external diameter or width of an object and tail is used to measure the depth if

an object.

How do we use the Vernier Callipers?

Step 1: Grip the object gently using the outside jaws of the callipers.

Step 2: Read the main scale on the immediate left of the zero mark on the vernier scale.

Step 3: Find the vernier mark which coincides with a marking on the main scale. Multiply it

with the least count it will give the reading of vernier scale.



Step 4: The length is found by adding the vernier scale reading to the main scale reading.

How do we avoid errors wen using the Vernier Callipers?

Before using the Vernier Callipers, we need to examine the instrument for zero error. That is,

we check if the zero mark on the main scale coincides with the zero mark on the sliding vernier

scale when the jaws touch each other. Below figure shows how to correct zero errors on the

Vernier Callipers.

Screw Gauge:

The micrometer screw gauge has main scale and a thimble/circular scale. It is usually used:

To measure objects that are two small to be measured with Vernier Callipers;

When measurements to a precision of 0.01 mm (i.e. 10 µm) are required.

A simple screw gauge consists of a U-shaped metal frame with a metal stud at its one end. A

hollow cylinder (or sleeve) has a millimeter scale over it along a line called index line parallel to

its axis. The hollow cylinder acts as a nut. It is fixed at the end of U-shaped frame opposite to

the stud. A thimble has a threaded spindle inside it. As the thimble completes one rotation,

the spindle moves 1 mm along the index line. This distance is called the pitch of screw gauge.

The thimble has 100 divisions around its one end. It is the circular scale of the screw gauge.

Least count of the screw gauge can be found as given below:



How do we use the micrometer screw gauge?

Step 1: Turn the thimble until the stud and the spindle are almost touching the object. Then,

turn the ratchet until it clicks. The click indicates that the grip of the screw gauge on the object

is just right for the reading to be taken.

Step 2: Read the main scale reading to the immediate left to the edge of the thimble.

Step 3: Take the thimble reading with the index line of the main scale. Each division on the

thimble scale is 0.01 mm.

Step 4: The diameter of the wire is found by adding the thimble reading to the main scale

reading.

How do we avoid errors when using the micrometer screw gauge?



Commonly used measuring instruments with their range and precision:

Mass Measuring Instruments:

Pots were used to measure grain in various part of the world in the ancient times. However,

balances were also in use by Greeks and Romans.

Beam balances are still in use at many places. In a beam balance, the unknown mass is placed

in one pan. It is balanced by putting known masses in the other pan.

Today people use many types of mechanical and electronic balances. Electronic balances are

more precise than beam balances and are easy to handle.

Physical Balance:

A physical balance is used in the laboratory to measure the mass of various objects by

comparison. It consists of a beam resting at the center on a fulcrum. The beam carries scale

pans over the hooks on either side. Unknown mass is placed on the left pan. Find some

suitable standard masses that cause the pointer to remain at zero on raising the beam.



How do we use a physical balance?

Step 1: Adjust the leveling screws with the help of plumb line to level the platform of physical

balance.

Step 2: Raise the beam gently by turning the arresting knob clockwise. Using balancing screws

at the ends of its beam, bring the pointer at zero position.

Step 3: Turn the arresting knob to bring the beam back on its supports. Place the given object

on its left pan.

Step 4: Place suitable standard masses from the weight box on the right pan till the pointer

rests at zero on raising the beam.

Step 5: Note the standard masses on the right pan. Their sum is the mass of the object on the

left pan.

Lever Balance:

A lever balance consists of a system of levers. When lever is lifted placing the object in one

pan and standard masses on the other pan, the pointer of the lever system moves. The pointer

is brought to zero by varying standard masses.

Electronic Balance:

Electronic balance come in various ranges; milligram ranges, gram ranges and kilogram ranges.

Before measuring the mass of a body, it is switched on and its reading is set to zero. Next

place the object to be weighted. The reading on the balance gives you the mass of the body

placed over it.

Measurement of Time:

Stopwatch:

A stopwatch is used to measure the time interval of an event. There are two types of

stopwatches; mechanical and digital.



A mechanical stopwatch can measure a time interval up to a minimum 0.1 second. Digital

stopwatches commonly used in laboratories can measure a time interval as small as 1/100

second or 0.01 second.

How to use a stop watch?

A mechanical stopwatch has a knob that is used to wind the spring that powers the watch. It

can also be used as a start-stop ad reset button. The watch starts when the knob is pressed

once. When pressed second time, it stops the watch while the third press brings the needle

back to zero position.

The digital stopwatch starts to indicate the tie lapsed as the start/stop button is pressed. As

soon as start/stop button is pressed again, it stops and indicates the time interval recorded by

it between start and stop of an event. A reset button restores its initial zero setting.

Measuring cylinder:

A measuring cylinder is a glass or transparent plastic cylinder. It has a scale along its length

that indicates the volume in millimeter (mL). Measuring cylinders have different capacities

from 100 mL to 2500 mL. They are used to measure the volume of a liquid or powdered

substance. It is also used to find the volume of an irregular shaped solid insoluble in liquid by

displacement method. The solid is lowered into a measuring cylinder containing water/liquid.

The level of water/liquid rises. The increase in the volume of water/liquid is the volume of the

given solid object.

How to use a measuring cylinder?

While using a measuring cylinder, it must be kept vertical on a plane surface. Take a measuring

cylinder. Place it vertically on the table. Pour some water into it. Note the reading while

keeping the eye at the same level as the meniscus of the liquid.

Measuring volume of an irregular shaped solid:

Measuring cylinder can be used to find the volume of a small irregular shaped solid that sinks

in water. Let us find the volume of a small stone. Take some water in a graduated measuring



cylinder. Note the volume Vi of water in the cylinder. Tie the solid with a thread. Lower the

solid into the cylinder till it is fully immersed in water. Note the volume Vf of water and the

solid. Volume of the solid will be Vf – Vi.

1.7 Significant Figures:

The value of a physical quantity is expressed by a number followed by some suitable unit.

Every measurement of a quantity is an attempt to find its true value. The accuracy in

measuring a physical quantity depends upon various factors:

The quality of the measuring instrument

The skill of the observer

The number of observations made

An improvement in the quality of measurement by using better instrument increases the

significant figures in the measured result.

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

More significant figure means greater precision.

Rules for finding the significant figures:

i. Non-zero digits are always significant.

ii. Zeros between two significant figures are also significant.

iii. Final or ending zeros on the right in decimal fraction are significant.

iv. Zeros written on the left side of the decimal point for the purpose of spacing the

decimal point are not significant.

v. In whole numbers that end in one or more zeros without a decimal point. These zeros

may or may not be significant. In such cases, it is not clear which zero serve to locate

the position value and which are actually parts of the measurement. In such a case,



express the quantity using scientific notation to find the significant zero. For example,

in the number 8200, it is not clear if the zeroes are significant or not. The number of

significant digits in 8200 is at least two, but could be three or four. To avoid

uncertainty, use scientific notation to place significant zeroes behind a decimal point:

8.200 × 103 has four significant digits

8.20 × 103 has three significant digits

8.2 × 103 has two significant digits

Rules for rounding in calculations:



Solved Exercise MCQ’s

1.1) Encircle the correct answer from the given choices.

i. The number of base units in SI are:

A. 3 B. 6 C. 7 D. 9

ii. Which one of the following unit is not a derived unit?

A. Pascal B. kilogram C. Newton D. Watt

iii. Amount of a substance in terms of numbers is measured in:

A. gram B. kilogramme C. Newton D. Mole

iv. An interval of 200µs is equivalent to:

A. 0.2 s B. 0.02 s C. 2 × 10-4 s D. 2 × 10-6 s

v. Which one of the following is the smallest quantity?

A. 0.01 g B. 2 mg C. 100 µg D. 5000 ng

vi. Which instrument is most suitable to measure the internal diameter of a test tube?

A. Metre rule B. Vernier Callipers C. Measuring tape D. Screw gauge

vii. A student claimed the diameter of a wire as 1.032 cm using Vernier Callipers. Upto what

extent do you agree with it?

A. 1 cm B. 1.0 cm C. 1.03 cm D. 1.032 cm

viii. A measuring cylinder is used to measure:

A. mass B. area C. volume D. level of a liquid

ix. A student noted the thickness of a glass sheet using a screw gauge. On the main scale, it

reads 3 divisions while 8th division on the circular scale coincides with index line. Its

thickness is:

A. 3.8 cm B. 3.08 mm C. 3.8 mm D. 3.08 m

x. Significant figures in an expression are:

A. all the digits

B. all the accurately known digits

C. all the accurately known digits and the first doubtful digit

D. all the accurately known and all the doubtful digits

Questions

1.2) What is the difference between base quantities and derived quantities? Give three

examples in each case.

Base quantities: Base quantities are the quantities on the basis of which other quantities are

expressed. There are seven physical quantities which form the foundation for other physical

quantities. These physical quantities are called the base quantities.

For example:

Length, mass, time, intensity of light, temperature, electric current and the amount of substance.



Derived quantities: The quantities that are expressed in terms of base quantities are called

derived quantities.

For example:

Area, volume, speed, force, work, energy, power, electric charge, electric potential, etc.

1.3) Pick out the base units in the following:

Joule, newton, kilogramme, hertz, mole, ampere, metre, kelvin, coulomb and watt.

1.4) Find the base quantities involved in each of the following derived quantities:

a) Speed:

Base quantities involved in speed are length and time.

b) Volume:

Base quantity involved in volume is length.

c) Force:

Base quantities involved in force are mass, length and time.

d) Work:

Base quantities involved in work are mass, length and time.

1.5) Estimate your age in seconds.

Suppose age = 15 years

(1 year = 365 days)

(1 day = 24 hours)

(1 hour = 60 minutes)

(1 minute = 60 seconds)

Use the following formula to convert your age into seconds:

1.6) What role SI units have played in the development of science?

SI system is used across the world. They have played very important role in the

development of science. Particularly this system is very useful to exchange the scientific

and technical information. Also manipulation in this system is quite easy i.e. the multiple

and sub multiple of different units are obtain simply by multiplying or dividing with ten or

power of tens.



1.7) What is meant by vernier constant?

The difference between one small division on main scale division and one vernier scale

division is 0.1 mm. It is called the vernier constant or least count (LC) of the Vernier

Callipers.

Least count of the Vernier Callipers can also be found as given below:

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

If the zero of both the scales of a given instrument do not coincide with each other it

means the given instrument has zero error. So our measurement will be less or greater

than the correct reading.

1.9) Why is the use of zero error necessary in a measuring instrument?

In order to get the correct measurement the use of zero error is necessary. The zero error

is the reading displayed when you know the true reading should be exactly zero. For

example, using a set of vernier callipers, the zero error is the reading that shows when the

callipers are fully closed. As long as you check for zero error, you can then use it to correct

your readings. Zero errors are of two types:

Positive zero error: Zero error will be positive if zero line of vernier scale is on the right

side of the zero of the main scale. To get the correct value zero error must be recorded

and subtracted from each reading.

Negative zero error: Zero error will be negative if zero line of vernier scale is on the left

side of zero of the main scale. To get the correct value zero error must be recorded and

added to each reading.

1.10) What is a stopwatch? What is the least count of a mechanical stopwatch you have used

in the laboratories?

Stopwatch is an instrument which is used to measure the time interval of an event. The

least count of mechanical stopwatch is 0.1 seconds.

1.11) Why do we need to measure extremely small interval of times?

In order to get the more accurate results we need extremely small interval of time as the

smaller is the time interval better resolution of measurement is possible.

1.12) What is meant by significant figures of a measurement?

All the accurately known digits and the first doubtful digit in an expression are called

significant figures. It reflects the precision of a measured value of a physical quantity.

1.13) How is precision related to the significant figures in a measured quantity?

The greater the number of significant figures, the greater the precision. Each significant

figures increases the precision by a factor of ten. An improvement in the quality of

measurement by using better instrument increases the significant figures in the measured

result.



Problems

1.1) Express the following quantities using prefixes.

a) 5000 g

(103 = 1 kilo)

b) 2000 000 W

(106 = 1 Mega)

c) 52 × 10-10 kg

d) 225 × 10-8 s

(10-6 = 1 micro)

1.2) How do the prefixes micro, nano and pico relate to each other?

As we know:

1 micro = 10-6

The relation between micro, nano and pico can be written as:

1 micro = 10-6

1 nano = 10-9 = 10-3 × 10-6 = 10-3 micro

1 pico = 10-12 = 10-6 × 10-6 = 10-6 micro

1.3) Your hair grow at the rate of 1 mm per day. Find their growth rate in nm per second.

Growth rate of hair in nm per second = 1 mm per day

Growth rate of hair in one day = 24 × 60 × 60 s = 86400 s

(Since 1 mm = 10-3 m and one day = 86400 s)

1.4) Rewrite the following in standard form.

a) 1168 × 10-27

1.168 × 103 × 10-27 = 1.168 × 103-27 = 1.168 × 10-24

b) 32 × 105

3.2 × 101 ×105 = 3.2 × 101+5 = 3.2 × 106

c) 725 × 10-5 kg

7.25 × 102 × 10-5 × 103 g = 7.25 × 102-5+3 g = 7.25 × 100 g = 7.25 g

d) 0.02 × 10-8

2 × 10-2 × 10-8 = 2 × 10-2-8 = 2 × 10-10

1.5) Write the following quantities in standard form.

a) 6400 km

6.4 × 1000 = 6.4 × 103 km



b) 380 000 km

3.8 × 100 000 = 3.8 × 105 km

c) 300 000 000 ms-1

3 × 100 000 000 = 3 × 108 ms-1

d) Seconds in a day

1 day = 24 × 60 × 60 s = 86400 s = 8.64 × 10 000 = 8.64 × 104 s

1.6) On closing the jaws of a Vernier Callipers, zero of the vernier scale is on the right to its

main scale such that 4th division of its vernier scale coincides with one of the main scale

division. Find its zero error and zero correction.

Main scale reading = 0.0 cm

Vernier division coinciding with main scale = 4th division

Vernier scale reading = 4 × 0.01 cm = 0.04 cm

Since zero of the vernier scale is on the right side of the zero of the main scale, thus the

instrument has measured more than actual reading. It is said to be positive error and its

zero correction will be negative.

Zero error = 0.04 cm

Zero correction = -0.04 cm

1.7) A screw gauge has 50 divisions on its circular scale. The pitch of the screw gauge is

0.5mm. What is its least count?

Number of division on circular scale = 50 divisions

Pitch of the screw gauge = 0.5 mm

Least count = ?

1.8) Which of the following quantities have three significant figures?

a) 3.0066 m

Zeros between significant digits are significant. Therefore, there are 5 significant figures in

3.0066 m.

b) 0.00309 kg

Zeros used for spacing the decimal point are not significant. Therefore, there are 3

significant figures in 0.00309 kg.

c) 5.05 × 10-27 kg

Only the digits before the exponent are considered, thus there are 3 significant figures in

5.05 × 10-27 kg.

d) 301.0 s

Final zeros or zeros after the decimal are significant. Therefore, there are 4 significant

figures in 301.0 s.



Hence, b and c has three significant figures.

1.9) What are the significant figures in the following measurements?

a) 1.009 m

Since zeros between two significant figures are significant, so there are 4 significant

figures.

b) 0.00450 kg

Zeros used for spacing the decimal point are not significant. Hence there are 3 significant

figures.

c) 1.66 × 10-27 kg

Only the digits before the exponent are considered, so there are 3 significant figures.

d) 2001 s

Since zeros between two significant figures are significant, so there are 4 significant

figures.

1.10) A chocolate wrapper is 6.7 cm long and 5.4 cm wide. Calculate its area upto reasonable

number of significant figures.

Length of chocolate wrapper = = 6.7 cm

Width of chocolate wrapper = = 5.4 cm

Area = = ?

Area = Length × Width

Answer should be in two significant figures because in data the least significant figures are

two therefore answer is 36 cm2.

Extra MCQ’s

Encircle the correct option i.e., A/B/C/D.

1. Prefixes are useful to express:

A. very small quantity B. very large quantity C. derived units D. both A and B

2. We study about matter, energy and their interaction in:

A. Biology B. Physics C. Chemistry D. Economics

3. By using prefixes, we can write 32 × 10-10 kg as:

A. 0.32 µg B. 32 µg C. 3.2 µg D. 320 µg

4. Significant digits in 0.058 are:

A. 4 B. 3 C. 2 D. 1



5. Study of internal structure of earth is:

A. geophysics B. electricity and

magnetism C. mechanics D. thermodynamics

6. Words or letters added before a unit and stand for multiples or sub-multiples of that unit are

called:

A. mass B. prefixes C. units D. rate

7. Least count of Vernier calipers is:

A. 0.01 mm B. 1 mm C. 0.01 cm D. 1 cm

8. Prefix for 109 is:

A. giga B. milli C. nano D. pico

9. All physical quantities are:

A. not measurable B. measurable C. related to each

other

D. not related to each

other

10. An interval of 300µs is equal to:

A. 0.3 s B. 3 × 10-4 s C. 3 × 10-6 s D. 0.03 s

11. An instrument used to measure small lengths such as internal or external diameter or length

of a cylinder, etc. is called:

A. vernier callipers B. physical balance C. screw gauge D. stop watch

12. Prefix for 4800000 W is:

A. 48 kW B. 480 kW C. 48 W D. 4800 kW

13. In screw gauge, distance between consecutive threads on spindle is:

A. 0.5 mm B. 0.01 mm C. 0.1 mm D. 1 mm

14. If zero line of vernier scale is on left side of zero of main scale, then zero error will be:

A. zero B. positive C. negative D. one

15. Significant digits in 3587 are:

A. 4 B. 3 C. 2 D. 1

16. To measure various physical quantities such as length, time, mass, volume, etc. we use:

A. mechanics B. measuring

instruments C. prefixes D. none of these



17. Least count of digital stopwatch is:

A. 0.2 s B. 0.1 s C. 0.3 s D. 0.01 s

18. If zero line of vernier scale is on right side of zero of main scale, then zero error will be:


19. Zeros used for spacing decimal point are:

A. non-significant B. significant C. imaginary D. negative

20. All accurately known digits and first doubtful digit in an expression are known as:

A. non-significant

figures B. significant figures C. estimated figures D. crossed figures

21. Final zeroes after decimal are:

A. non-significant B. significant C. worthless D. none of these

22. Least count of physical balance is:

A. 0.0001 g B. 0.001 g C. 0.01 g D. 1 g

23. A refrigerator is made on principles of:

A. heat B. atomic physics C. plasma physics D. thermodynamics

24. Distance of moon from earth is:

A. 3.84 × 108 m B. 100 km C. 1000 km D. 2000 km

25. In screw gauge a thimble around its one end has:

A. 50 divisions B. 250 divisions C. 100 divisions D. 10 divisions

26. One division of Vernier scale is of:

A. 1 cm B. 1 mm C. 0.9 cm D. 0.9 mm

27. Unit which is not derived is:

A. newton B. kilogram C. watt D. pascal

28. Base quantity among following is:

A. electric charge B. amount of substance C. area D. volume

29. Smallest measurement an electronic balance can take is:

A. 0.01 g B. 0.001 g C. 0.0001 g D. 0.00001 g



30. A modified type of beam balance used to measure small masses by comparison with greater

accuracy is known as:

A. measuring balance B. electronic balance C. physical balance D. balance

31. Science deals with study of non-living things is known as:

A. physical science B. formula science C. biological science D. fundamental science

32. A graduated glass cylinder marked in milliliters is called a:

A. screw gauge B. vernier callipers C. measuring cylinder D. physical balance

33. Word ‘Science’ is derived from a Latin word:

A. scientific B. significant C. scientia D. scientism

34. Study of fourth state of matter is called:

A. nuclear physics B. plasma physics C. nano physics D. quantum physics

35. Peter claimed that diameter of a wire is 1.042 using vernier callipers. Up to what extent he is

right?

A. 1 cm B. 1.0 cm C. 1.04 cm D. 1.042 cm

36. Study of motion of objects, its causes and effects is called:

A. heat B. mechanics C. atomic physics D. plasma physics

37. By converting 3 700 000 watt into kilowatt, we get:

A. 3.7 W B. 3700 kW C. 37000 kW D. 37 kW

38. A chips wrapper is 4.5 cm long and 5.9 cm wide. Its area up to significant figures will be:

A. 30 cm² B. 28 cm² C. 26.55 cm² D. 32 cm²

39. A worldwide system of measurements in which the units of base quantities were introduced

is called:

A. CGS B. international

system of units C. SGS D. none of these

40. “seconds in a day” can be written in standard form as:

A. 864 × 104 s B. 86.4 × 104 s C. 8640 × 104 s D. 8.64 × 104 s

41. Least count of screw gauge is:

A. 0.1 mm B. 0.01 mm C. 0.2 mm D. 0.02 mm



42. Number 0.0000548 can be represented in scientific notation as:

A. 5.48 B. 548 C. 5.48 × 10-5 D. 54.8

43. Non-zero digits are always:

A. significant B. non-significant C. worthless D. none of these

44. Quantities on basis of which other quantities are expressed are called:

A. prefixes B. base quantities C. derived quantities D. quartile quantities

45. To measure volume of a liquid, powdered substance or irregular shaped insoluble solid we

can use:

A. measuring cylinder B. screw gauge C. vernier callipers D. physical balance

46. In screw gauge, if zero of circular scale has crossed the index line, then zero error will be:


47. A way to express a number as a number between 1 and 10 having an appropriate power is

called:

A. scientific notation B. prefix C. base units D. derived units

48. Least count of ruler is:

A. 2 mm B. 10 mm C. 50 mm D. 1 mm

49. By converting 30,000 grams into kilograms, we get:

A. 30 kg B. 3 kg C. 300 kg D. 0.3 kg

50. While measuring length eye must be kept:

A. above the scale B. at an acute angle C. horizontal with

scale D. below the scale

51. 1.35 can be rounded to:

A. 1.3 B. 1.4 C. 1.5 D. 1

52. Number of base units in SI are:

A. 4 B. 7 C. 6 D. 9

53. When a standard is set for a quantity, then standard quantity is called a:

A. amount B. rate C. prefix D. unit

54. Physical sciences were divided into:

A. 4 disciplines B. 3 disciplines C. 5 disciplines D. 6 disciplines



55. Significant digits in 275.00 are:

A. 2 B. 3 C. 4 D. 5

56. Study of structure and properties of atoms is called:

A. atomic physics B. mechanics C. plasma physics D. geophysics

57. Units used to measure derived quantities are known as:

A. square units B. derived units C. base units D. none of these

58. Study of nature of heat, modes of transfer and effects of heat is studied under branch

named as:

A. mechanics B. Light C. heat D. atomic physics

59. To measure small lengths such as diameter of a wire, thickness of a metal sheet, etc. We

use:

A. physical balance B. screw gauge C. vernier callipers D. stop watch

60. We study physical aspects of sound waves, their production, properties and applications

under branch named as:

A. sound B. atomic physics C. plasma physics D. heat

61. Amount of a substance in terms of numbers is measured in:

A. gram B. kilogram C. mole D. newton

62. To measure time interval of an event, we use:

A. screw gauge B. physical balance C. vernier callipers D. stop watch

63. Study of production, properties of iconic state of matter is called:

A. atomic physics B. plasma physics C. mechanics D. nuclear physics

Extra Questions

Q1) How can you differentiate between base and derived quantities?

Base Quantities Derived Quantities

There are seven physical quantities which form

the foundation of other physical quantities.

These are known as base quantities.

Those physical quantities which are expressed

in terms of base quantities are called derived

quantities.

Length, mass, time, electric current, amount of

substance, intensity of light and temperature.

Area, volume, speed, force, work, energy,

power, electric charge, etc.



Q2) Define physical quantities with examples.

All measureable quantities are called physical quantities such as length, mass, time and

temperature. A physical quantity possesses at least two characteristics in common. One is

its numerical magnitude and the other is the unit in which it is measured.

Q3) The Sun is one hundred and fifty million kilometers away from the Earth. Write this

(a) as an ordinary whole number.

(as kilo = 103)

(b) in scientific notation.

Q4) Write the numbers given below in scientific notation.

(a) 3000000000 ms-1

= 3.0 × 109 ms-1

(b) 6400000 m

= 6.4 × 106 m

(c) 0.0000000016 g

= 1.6 × 10-9 g

(d) 0.0000548 s

= 5.48 × 10-5 s

Q5) What do you mean by measuring instruments. Write some name of measuring instrument used in physics.

Measuring instruments are used to measure various physical quantities such as length, mass, time, volume, etc. Measuring instruments used in the past were not so reliable and accurate as we use today. Some of the measuring instruments used in physics laboratory are:

Meter rule, measuring tape, vernier callipers, screw gauge, physical balance, stop watch, measuring cylinder.

Q6) Which one of the two instruments is more precise and why?

a) Vernier Callipers b) Screw Gauge

The least count of vernier callipers is 0.01 cm while the least count of screw gauge is 0.001 cm.

The vernier callipers measure the length with an accuracy of 0.01 cm. The screw gauge measures the length with an accuracy of 0.001 cm. Therefore, screw gauge is more precise instrument.



Q7) What is the function of balancing screws in physical balance?

Function of the balancing screws is to balance the pans of the physical balance. We use balancing screws to remove the zero error of the physical balance. Balancing screws in a physical balance is used to bring the pointer at zero position.

Q8) On which pan we place the object and why?

We place the object in left pan because standard masses are placed on the right pan. So only for convenience we put the weights on the right pan after keeping object on the left pan.

Q9) Covert the following:

a) 10 km/h into m/s

b) 100 μm into nm

c) 5 litre into m3

Q10) What are the factors on which the accuracy in measuring physical quantity depend?

The accuracy in measuring a physical quantity depends upon various factors:

The quality of the measuring instrument The skill of the observer The number of observations made

Q11) On closing the stud and spindle of a screw gauge, the zero of the circular scale is behind the index line and 8th division of the circular scale coincides with the index line. There are 50 divisions on the circular scale and the distance between two consecutive threads on the spindle is 0.5 mm. Find its zero error and zero correction.

Closing the gap of the screw gauge

Main scale reading = 0.0 mm

Least count =

Circular scale reading = 8 × 0.01 mm

= 0.08 mm

Zero error of the screw gauge = 0 mm + 0.08 mm

= + 0.08 mm

Zero correction Z.C. = - 0.08 mm

Q12) Which safety equipments a school laboratory must have?

A school laboratory must have safety equipment such as:



Waste-disposal basket Fire extinguisher Fire alarm First Aid Box Sand and water buckets Fire blanket to put off fire Substances and equipments that need extra care must bear proper warning

signs such given below:

Q13) How can we measure the volume of an irregularly shaped solid?

Measuring cylinder can be used to find the volume of a small irregular shaped solid that

sinks in water. Let us find the volume of a small stone. Take some water in a graduated

measuring cylinder. Note the volume Vi of water in the cylinder. Tie the solid with a thread.

Lower the solid into the cylinder till it is fully immersed in water. Note the volume Vf of

water and the solid. Volume of the solid will be Vf – Vi.

physical quantities and measurement · step 3: take the thimble reading with the index line of the...

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