Physics For Class X Chapter No. 2 - Questions And Answers

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MEASUREMENT

Questions And Answers

IMPORTANT QUESTIONS OF PAST PAPERS

• Write S.I units of the following physical quantities: (i)Length (ii) Electric current (iii) Pressure (iv) Work (v)Volume (vi) Force (2013)
• Write down S.I.U for the following (i)Viscosity (ii) Stress (iii)Torque (iv)Temperature (v)Momentum (vi)Input (2014)
• Write the approximate value of mass of our galaxy, earth and moon. (2015)
• Write down the S.I units of the following physical quantities: (i)Time (ii)Weight (iii)Power (iv)Stress (v)Length (vi)Frequency (2017)
• The radius of Hydrogen atom is 0.53 X 10^-10m. Convert it in Kilometer, millimeter, micrometer and nano meter (2018)

Note: No question in 2009, 2010, 2011, 2016.

Questions / Answers

Q.1:What is meant by Measurement? What are the importance pf measurement?
Ans: MEASUREMENT: The following information about a body or an event is called Measurement.

• Size and nature of a body is described with a scale.
• A clock describes an event.
• Hence the reading will give the scale or clock about a body or an event is known as Measurement.

IMPORTANCE OF MEASUREMENT:

• In our daily life we get knowledge of things through our five senses, touch, smell, taste, sight and hearing. However our sense often do not provide us with correct information.
• We use measuring devices generally called apparatus to get the correct measurement. Such as:
• To measure volume we use a measuring cylinder.
• For mass, we use a common balance.
• For the measurement of length a meter scale is used.
• A vernier caliper can measure correctly up to 0.1 mm and a micrometer screw gauge can measure correctly up to 0.1 mm.
• Any instrument whose calibration is in doubt must be checked or discarded.

Q,2:Define the term Unit.
Ans: UNIT: Such quantities that are used to express physical quantities are called Unit. Without standardized units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way.

Q.3:Define physical quantities? write down its type?
Ans: PHYSICAL QUANTITIES:
Every material has certain characteristics. These are to be measured to specify them. For instance, if we want to specify the characteristics of a brick we will have to measure its length, width, height and mass. Such characteristics are called physical quantities.

TYPES OF PHYSICAL QUANTITIES:

• Fundamental quantities
• Derived quantities

FUNDAMENTAL QUANTITIES:
Fundamental quantities length, mass and time are supposed to be the main physical quantities. All physical quantities in mechanics can be express in the terms of fundamental quantities.
For example: Time, mass, temperature, length, current.

DERIVED QUANTITIES:
The physical quantities that are derived from fundamental quantities are called derived quantities. The derived quantities are obtained from simple multiplication and division of fundamental quantities.
For Example Speed, volume, force, work, pressure.

Q.3: Define fundamental or basic and derived units? OR Write down the name of fundamental and derived quantities with their units in S.I. system and their symbols?
Ans: FUNDAMENTAL OR BASIC UNITS:
The international system of units (S.I.units system) is based on seven independent units in known as fundamental or basic units. These units used to express fundamental quantities

Fundamental Or Basic Quantities With Their Units

S.No.	Physical quantity	Symbol of quantity	Name of Units	Symbol of units
1.	Length	l	Meter	m
2.	Mass	M	Kilogram	kg
3.	Time	t	Second	s
4.	Electric Current	I	Ampere	A
5.	Temperature	T	Kelvin	K
6.	Luminous Intensity	Iv	Candela	d
7.	Amount of substance	n	Mole	mol

DERIVE UNIT: The units of other physical quantities, which are derived from fundamental units, are called Derived Units. These units are obtained by multiplication and/or division one or more fundamental units.

DERIVED QUANTITIES WITH THEIR UNITS

S.No.	Physical quantity	Symbol of quantity	Name of Units	Symbol of units
1.	Speed	v	meter per second	m/s or ms-1
2.	Acceleration	a	meter per second square	m/s2 or ms-2
3.	Volume	V	cubic meter	m3
4.	Force	F	Newton	N {Kg m/s2}
5.	Pressure	P	Pascal	Pa { N/m2 or Nm-2}
6.	Work	W	Joule	J {Nm}
7.	Charge	Q	Columb	C

Q.4: Give the difference between fundamental unit and derived unit?

Ans: DIFFERENCE BETWEEN FUNDAMENTAL UNIT AND DERIVED UNIT

S.No.	Fundamental unit	Derived Unit
1.	The physical quantities discovered from first hand knowledge are called fundamental units.	The unit of those physical quantities which are derived from fundamental physical quantities are called derived units.
2.	Fundamental units cannot be further reduced to elementary level; in fact, these are elementary units.	Derived units can be reduced to its elementary level, which are composed of fundamental units.
3.	Fundamental units cannot be expressed in terms of derived units.	Derived units can be expressed in terms of fundamental units.
4.	Only seven fundamental units exist in Metric System or SI system.	There exist a large number of derived units in Metric System.
5.	Examples of fundamental units are Length (Meter, m), Mass (Kilogram, kg), Time (Second, s), Temperature (Kelvin, K), Amount of substance (Mole, mole), Electric current (Ampere, A), Luminous intensity (Candela, cd)	Examples of few derived units are Velocity (m/s), Acceleration (m/s2), Momentum (kg m/s ), Force (N), Density (kg/m3), Energy (J), Power (W), etc.

Q.5: Define scalar and vector quantity with examples.
Ans:

• Scalar quantity: Physical quantities, which are completely specified by their magnitude only, are called scalar quantities. it is denoted by ( ⎼ ) .
  Example: Time, Mass, Distance, Work, Energy, Temperature etc.
  
  
• Vector quantity: Physical quantities, which are completely specified by their magnitude and direction both, are called vector quantities. It is denoted by ( → ) .
  Example: Displacement, Velocity, Acceleration, Force, Weight, Torque, Momentum etc.

Q.6: Define inversely, directly proportional and proportional constant.
Ans: INVERSELY PROPORTIONAL:
Two physical quantities are said to be inversely proportion, if one quantity increases with the decrease in the other quantity or one is decreases with the increase in other. The ratio of these physical quantity will be a constant. The graph between them is a curved line.

V œ ¹⁄_T

DIRECTLY PROPORTIONAL:
Two physical quantities are said to be directly proportional, if one quantity increases with the increase in other physical quantity or one is decreases withe the decrease in other. The product of these quantities will be a constant. The between them is a straight line.

V œ T

PROPORTIONAL CONSTANT:
To change the symbol of inversely or directly proportional between two physical quantities we must use a symbol K, which is called proportional constant.

Q.7: Write down the units of the following quantities.
Ans:

S. No.	Quantity	Unit
1.	• Length = l	Meter = m
2.	• Mass = m	Kilogram = kg
3.	• Time = t	Second = S
4.	• Current = I	Ampere = A
5.	• Speed = S	Meter per sec = ms-1
6.	• Volume = V	Cubic meter = m3
7.	• Acceleration = a	Meter per sec-2 = ms-2
8.	• Force = F	Newton = N
9.	• Work = W	Joule = j
10.	• Charge = q	Coulomb = C
11.	• Velocity = V	Meter per sec = ms-1
12.	• Distance = S, d	Meter = m
13.	• Height = h	Meter = m
14.	• Gravity = g	Meter per sec-2 = ms-2
15.	• Tension = T	Newton = N
16.	• Weight = W	Newton = N
17.	• Radius = r	Meter = m
18.	• Gravitational Constant	Nm2 /Kg2
19.	• Kinetic Energy = K.E	Joule = j
20.	• Power = P	Watt = W
21.	• Potential energy	Joule = j
22.	• Effort = p	Newton = N
23.	• Stress	N / m2
24.	• Pressure = P	N / m2
25.	• Frequency = f	Hazard = Hz
26.	• Wavelength = λ	µF
27.	• Capacity of the capacitor	9 x 10-31kg
28.	• Potential difference	Volt = V
29.	• Resistance = R	Ohms = Ω
30.	• Torque = ɽ	Newton Meter = Nm

Prepared By: Sir Waseem

Notes By Adamjee Coaching Center

Q.1: What is measurement? What is the importance of measurement?
Ans: MEASUREMENT:
The meaning of measurement is the comparison of an unknown quantity with a standard, to see how many times it is big or small as compared to the standard.

Importance Of Measurement:
In our daily life we get knowledge of things through our five senses, touch, smell, taste, sight and hearing. However our sense often do not provide us with Correct information.
We use measuring devices generally called apparatus to get the correct measurement. To measure volume we use a measuring cylinder. For mass, we use a common balance and for the measurement of length a meter scale is used. A vernier caliper can measure correctly up to 0.1 mm and a micrometer screw gauge can measure correctly up to O.l mm. Any instrument whose calibration is in doubt must be checked or discarded.

Q.2: What is a system units? How many system are there, define each?
Ans: SYSTEM OF UNITS:
A set of fundamental and derived units is called a system of units.

TYPES OF SYSTEM OF UNITS:
There are four system of units being used in scientific work.

1. M.K.S System:
   In MKS system length, mass, and time are fundamental quantities and their units are meter, kilogram and second.
   
   
2. C.G.S System:
   In CGS system the fundamental quantities are length, mass and time and their units in this system are centimetre, gram and second.
   
   
3. F.P.S System:
   In FPS system the fundamental quantities are length, force and time and their units in this system are foot,pound,and second. It is also call British Engineering System.
   
   
4. Basic S.I. Units:
   In 1991, an international conference was held near Paris, where it was recommended that a system known as System International (S.I.) Units be introduced and used all over the world. Unit of seven quantities are taken as basic units which are called fundamental units. These are:
   (i) Unit for Length is meter.
   (ii) Unit for Mass is Kilogram.
   (iii) Unit for Time is Second.
   (iv) Unit for Current is Ampere.
   (v) Unit for Temperature is Kelvin.
   (vi) Unit for Luminous intensity is Candela.
   (vii) Unit for Amount of substance is mole.

Q.3: Define standard of length - meter?
Ans: STANDARD OF LENGTH - METER:
The meter is the length of the path traveled by light in vacuum during a time interval of  1 / 299,792,458 of a second.

OR

Meter is also define as the distance between two marks engraved on an iridium - platinum alloy bar kept at 0℃ in the international bureau of weights and measures near Paris.
1 meter = 1650763.73 wavelengths of krypton (Kr) atom in a vacuum.

The multiples and sub-multiples units of a meter are very easily obtained by multiplying and dividing it by 10 as follow:

(kilometer = km, meter = m, centimeter = cm, millimeter = mm, micrometer = µm, nanometer = nm)

Q.4: Give some Important length which was calculated by scientists?
Ans: SOME IMPORTANT MEASURED LENGTH:

Approximate Values

Length	Meters
Farthest observed quasar	2 x 1026 m
Andromeda galaxy	2 x 1022 m
Radius of galaxy	6 x 1019 m
The nearest star (Proximal Centauri)	4 x 1016 m
The orbit radius of planet Pluto	6 x 1012 m
Radius of the sun	7 x 108 m
Radius of the earth	6 x 106 m
Radius of hydrogen atom	5 x 10-11 m
Effective radius of proton	2 x 10-15 m

Q.5: How do we covert the following:

• Centimeter into Millimeter and Meter.
• Meter into Centimeter, Millimeter and nanometer.
• Kilometer into meter.

Ans: Centimeter converts into Millimeter and Meter.

• When cm converts into mm we will multiply cm value by 10
• When cm converts into m we will cm value multiply by ¹⁄₁₀₀ or 10^-2 OR divide cm value by 100.

Meter converts into Centimeter, Millimeter and nanometer.

• When m converts into cm we will multiply m value by 100 or 10²
• When m converts into mm we will multiply m value by 1000 or 10³
• When m converts into nm we will multiply m value by 10⁹

Kilometer converts into meter.

• When km converts into m we will multiply km value by 1000 or 10³

Q.6: Define standard of mass — kilogram?
Ans: KILOGRAM:
One kilogram is the mass of specific dimension of platinum - iridium alloy cylinder which is kept in the International Bureau of Weights and Measures near Paris. It is taken to be the standard one kilogram.
Few of its Multiples and sub multiples are given below:

Q.7: Give some important masses which was calculated by scientists?
Ans: SOME MEASURED MASSES:

(Approximate Values)

Object	Kilogram
Known universe	1035 kg
Our Galaxy	2 x 1043 kg
The sun	2 x 1023 kg
Earth	6 x 1024 kg
Moon	7 x 1022 kg
Speck of dust	7 x 10-10 kg
Virus	1 x 10-15 kg
Uranium atom	4 x 10-26 kg
Proton	2 x 10-27 kg
Electron	9 x 10-31 kg

Q.8: Converts Gram into Milligram, Microgram and Kilogram.
Ans: Gram Converts into Milligram, Microgram and Kilogram

• When gram converts into mg we will multiply gram value by 1000 or 10³
• When gram converts into µmg we will multiply gram value  by 1000 000 or 10⁶
• When gram converts into kg we will multiply gram value by¹⁄₁₀₀₀  or 10^-3 or divide it by 1000 or 10³

Q.9: Define standard of time - second?
Ans: STANDARD OF TIME - SECOND:
For scientific work, the second was earlier defines as ¹ / _86,400th part of a mean solar day.
Now, a second is defined in terms of a time period of vibration of a Cesium atom of mass number 133 (Cs-133). one second is 9,192,631,770 period of vibration of Cs-133 This unit of time is ascertained through Cesium atomic clock. one such clock is at National Bureau of Standards, Washington, U.S.A.
Its related Multiples and sub multiples are given below:

1 hr. (hour) = 60 minute = 60 X 60 s = 3600 s

1 min (minutes) = 60 s (seconds) = ¹ / ₆₀ hr. 

1 s (second) = ¹ / ₆₀ min = ¹ / ₃₆₆₀ hr.

1 ms (millisecond) = ¹ / ₁₀₀₀ s = 1000^-3 s

1 µs (microsecond) = ¹ / _{1,000 000} s= 10^-6 s

1 ns (nanosecond) = ¹ / _{1,000 000 000} s = 10^-9s

Q.10: Give some important times which was calculated by scientists?
Ans: SOME MEASURED TIME:

(Approximate Values)

Time Interval	Seconds
Life time of proton	> 1040 sec.
Age of universe	5 x 1017 sec.
Time of earth's orbit around the sun (1 year)	3 x 107 sec.
Time of earth's rotation about its axis (1 day)	9 x 104 sec.
Time between normal heart beats	8 x 10-1 sec.
Period of oscillation of 3cm microwave	1 x 10-10 sec.
Life time of least stable particles	< 10 -23 sec.

Q.11: What are the advantages of S.I. units?
Ans: ADVANTAGES OF SI UNITS:

• These units are used all over the world as a standard of units.
• Mathematical calculations in these unit are easier because smaller and bigger units can be obtained just by a simple division or multiplication by a factor of ten.
• For larger and smaller quantities we can use prefixes with the units.
• Prefixes for factors greater than unity have Greek roots.
• Prefixes for factors less than unity have Latin roots.

Q.12: Give some S.I. prefixes?
Ans: S.I. PREFIXES:

Prefix	Symbol	Factor
Exa	e	1018
peta	p	1015
Tera	t	1012
Giga	g	108
Mega	m	106
Kilo	k	103
Hecto	h	102
Deka	da	10
Deci	d	10-1
Centi	c	10-2
Milli	m	10-3
Micro	µ	10-6
Nano	n	10-9
Pico	p	10-12
Femto	f	10-15
Atto	a	10-18

Q.13: What are significant figures or digits in a number or reading? What are the rules for determining significant figures in a number?
Ans: SIGNIFICANT FIGURES:
A significant figure is one, which is known to be reasonable and reliable.
The digit required o express a number on the same accuracy as the measurement is represents, is known as "Significant figures".

OR

Any measurement of the accurately known digits and the first doubtful digit are called significant figures of that number.
Example:
In measuring the length of an object with a meter scale, the smallest reading that can be made directly is 0.1 cm, i.e. the least count of the scale. If some one measure the length of a object as 24.3 cm, than all the three numbers 2, 4 and 3 are significant figures.
On the other hand, If someone writes the length of the object as 24.35 cm, than 2, 4 and 3 are significant figure. 5 indicates an error which may be positive or negative i.e., error is + (0.05).
  
Rules for determining significant figures of a number:

1. All non-zero digits in a number are significant figure, e.g. In 123 has three significant figures 1, 2 and 3.
2. If zero is between non-zero digits, it is counted as significant figures, e.g. 7003, 40.71 and 2.503 all have four significant figures.
3. Zero on the right of the significant are not counted, e.g. In 3100, significant figures are 2.
4. Zero on the left of significant figure or appearing in front of all non - zero digits are not counted. They are acting as place holder. e.g. 0.0081, 0.56, 0.00033 all have two significant figures.
5. Zeros on the right of a fractional number are counted, e.g. in 10.24 significant figure are four.
6. In addition, subtraction, multiplication and division, the number of significant figure of the result is reduced in the smallest number of significant figure of the number to value in calculation.
   e.g. 3.142 X 2.7
   = 8.4834
   = 8.5 (reduced in low significant figure).

Q.14: What is scientific notation
Ans: SCIENTIFIC NOTATION:
Scientists often work with very large and very small measurement for example the mass of the earth is about 6,000060,000000,000,000000000 kg. In this form the measurement take up much space and are difficult to use in calculation. To work with such measurement more easily we can write them in a shortened form by expressing decimal places as powers of ten. This method of expressing numbers is called exponential notation.
Scientific notation is based on exponential notation. In scientific notation the numerical part of a measurement is expressed as the product of a number between 1 and 10 and whole number power of ten.

M X 10ⁿ

In this expression 1 < M < 10 and n is an integer. For example two kilometres can be expressed as

2 X 10³ m.

MEASURING INSTRUMENTS

Q.15: What is vernier calipers? What are its major parts? OR Write down the construction and working of Vernier calipers?
Ans: Vernier calipers:
is a meter stick graduated in millimeters used to measure a distance up to 1 mm. It can also be used to measure a distance up to 0.05 mm.

Parts Of Vernier Scale:
Vernier Calipers consists of

1. A pair of calipers having a Main Scale and Vernier Scale.
2. Jaws.
3. Thin Flat Rod.

CALIPERS:
Main Scale (MS):

• A vernier scale consists of a rectangular steel bar whose one side (smaller lines) is graduated in millimeters and the longer lines on the main scale represent centimeter.
• Each division on the main scale is 1 mm (0.1 cm).
• Its left upper part has a jaw "A".

Vernier Scale (VS):

•  A small scale usually consisting of 10 division which slides over the main scale is known as vernier scale.
• The left upper part of this scale has a jaw "B".

Jaws:

• It has two jaws "A" and "B", which are also called callipers.
• Jaw "A" is fixed on the rectangular bar while jaw "B" is slides over the main scale and is provided with a vernier scale.
• When jaw "A" and "B" touch each other, the zero of the vernier scale coincides with zero of the main scale. Its mean there is no zero error.

Thin Flat Rod:

• A thin flat rod is attached to the sliding scale on its back which can measure the internal depth of a hallow cylinder.

WORKING OR USE OF VERNIER CALLIPERS:

1. The diameter of a small sphere object can be measured with the help of this device.
2. Before the measurement close the jaws of the vernier callipers completely and note down whether the zero line of the vernier scale coincides with the zero of the main scale.
3. If they coincide, there is no zero error.
4. Open the jaws "A" and "B" and introduce the metallic cylinder between them, Move the jaws "B" towards the cylinder, so that the cylinder is held tightly between jaws.
5. Note the main scale reading just before the zero of the vernier scale. Check, which division of the vernier scale exactly coincides with any division of the Main scale.
6. Repeat the Value three time and note down these observation in the following table.
7. Least count (L.C.) of the vernier calliper is 0.01 cm.

OBSERVATION TABLE

Number of Observations	Main Scale Reading M cm	Vernier Scale Reading V cm	Fractional Part F.P. = V X L.C. cm	Diameter or length =M + F.P. cm
1	1.9	4	4 X 0.01 = 0.04	1.9 + 0.04= 1.94

Q.16: Draw the neat and labelled diagram of Vernier callipers and show all the major parts on it?
Ans: Diagram Of Vernier Callipers:

Q. 17: Define vernier constant or least count of vernier calipers? How it is calculated?
Ans: Vernier Count (VC) or Least Count (LC) of Vernier calipers:
Vernier scale has 10 divisions of total length as that of "9" on Main scale division i.e. 9 mm. Hence the difference on length between a main scale division and a vernier scale division is 1 - ⁹ / ₁₀ = 1 - 0.9 = 0.1 mm or 0.01 cm. This difference is the smallest length measurable with vernier and is term as vernier constant or least count.

OR

The minimum measurement that can be made with the help of a vernier calipers is known as least count of vernier calipers or vernier count (VC).

Q.18: Define Zero Error ? Write down its types?
Ans: ZERO ERROR:
On closing the two jaws "A" and "B", if the zero of the main scale does not coincide with the zero of the vernier scale , then the instrument has an error called zero error.
There ere two types of zero error:

1. Positive zero error
2. Negative zero error

1- Positive Zero Error:
If the zero of the vernier scale is on the right side of the zero of the main scale, then the zero error will be positive.
To calculate this zero error, check the vernier scale division (E) which exactly coincide with any main scale division. Then,

Zero error (Z.E) = E X L.C

In case of positive error, it is subtracted from the total reading.

2- Negative Zero Error:
If the zero of the vernier scale is on the left side of the zero of the main scale, then the zero error will be negative.
To calculate this zero error, check the vernier scale division (E) which exactly coincide with any main scale division. Then,

Zero error (Z.E) = (10 - E) X L.C

In case of negative error, it is added to the total reading.

Q.19: Define micrometer screw gauge? Write down its major parts? Or Write down the construction and working of micrometer screw gauge?
Ans:MICROMETER SCREW GAUGE:
A micrometer screw gauge used to measures very small lengths such as the diameter of a wire or sphere so as to get readings accurate up to 3^rd or 4^th place of decimal. It can measure accurately up to one hundredth part of a millimetre.

OR

It is an instrument that can measure small length or thickness correctly up to  ¹ / ₁₀₀₀  of millimetre or up to three place of decimals.

Construction:
Major Parts:
It consists of:

• U - shaped metallic frame
• Fixed stud
• Movable stud
• Main scale
• Circular scale
• Drum
• Ratchet

U - shaped metallic frame having a fixed stud at one end, while a screw passes through the other end and has a hallow cylinder. A millimetre scale is graduated on the fixed nut of the hallow cylinder along a line which is parallel to its axis. This scale is known as Main scale.
The hallow cylinder act as a nut. The screw has a movable end. A cap called ratchet is provided at the end of the screw and it can be rotated to move the screw forward or backward. The left end of this cap has a circular scale which is usually divided into 100 or 50 equal divisions.

Working Of Micrometer Screw Gauge:

• Bring the spindle and the anvil together without applying undue pressure. If the zero of the circular scale is in with the reference line on the main scale, there is no zero error.
• Place the small sphere between the spindle and the anvil and turn the screw, so that the sphere is held between them without any undue pressure.
• Note the reading on the main scale in front of cap and the division of circular scale which exactly coincides with the reference line of the main scale.
• L.C of micrometer screw gauge = 0.001 cm

OBSERVATION TABLE

Number of Observations	Main Scale Reading M cm	Circular Scale Reading C cm	Fractional Part F.P. = C X L.C. cm	Diameter or length D=M + F.P. cm
1	0.4	74	74 X 0.001 = 0.074	0.4 + 0.074= 0.474

Q.20: Draw neat and labeled diagram of screw gauge and show the name of all part?
Ans: DIAGRAM:

Q.21: Derive a relation between pressure and volume?
Ans: Relation Between Pressure and Volume:
If we increase the pressure in a cylinder, then the volume of the gas inside the cylinder will decrease.
Therefore pressure (P) and volume (V) are inversely proportional to each other.

V ∝ ¹ ∕ _P

V = ^(constant) ∕ _P

PV = constant

If K = constant

than PV = K

If we draw a graph between volume and pressure, we will take the pressure (P) along the X-axis and the volume (V) along the Y-axis, then we get a slide curve.