9th Class Physics Chapter 1 Physical Quantities and Measurements Long Questions

Q: Write a note on the metre rule. How is parallax error avoided?

The metre rule A metre rule is a scale one metre long, marked in centimetres and millimetres. It is used in the laboratory to measure lengths such as the length of a table, a book or a rod. Least count of a metre rule: 1 mm (0.1 cm): the smallest length it can measure correctly. How to measure a length Place the rule along the object, touching it.; Line up the zero mark with one end of the object.; Read the mark at the other end with your eye directly above it.; The reading at the other end is the length. Parallax error If the scale is read from the side, the mark appears to shift and the object seems longer or shorter than it is. This is parallax error. Keep the eye directly above the mark, at right angles to the scale.; Keep the object touching the scale, or stand the rule on its edge so the marks touch the object. If the end of the rule is worn

Q: Describe the construction and working of Vernier Callipers.

Introduction Vernier Callipers measure small lengths precisely, to 0.1 mm (0.01 cm): the diameter of a pipe or a coin, the inner size of a test tube, or the depth of a beaker. Construction Main scale: fixed, marked in millimetres.; Vernier scale: slides along the main scale; it is 9 mm long and divided into 10 equal divisions.; Outside jaws: one fixed, one sliding; they grip an object to measure its outer size.; Inside jaws: on the top; they fit inside an object to measure its inner size.; Depth rod (tail): slides out of the end to measure depth.; Lock screw: holds the vernier in place while you read it. Least count 1 main scale division = 1 mm, and 10 vernier divisions = 9 mm, so 1 vernier division = 0.9 mm. LC = 1 MSD − 1 VSD = 1 mm − 0.9 mm = 0.1 mm = 0.01 cm Working: taking a reading Close the jaws and check for zero error.; Hold the object gently between the outside jaws.; Main scale reading (MSR): read the main scale mark just before the vernier's zero.; Vernier reading: find the vernier line (n) that lines up exactly with a main scale line.; Reading = MSR + (n × LC); then correct for any zero error. Reading = 2.3 cm + (7 × 0.01 cm). 2.37 cm Zero error and its correction No zero error, The two zeros line up exactly, 0; Positive, Vernier zero is to the right of the main zero, + (n × LC); Negative, Vernier zero is to the left of the main zero, − (10 − n) × LC Corrected reading = observed reading − zero error Digital Vernier Callipers show the reading on a screen and have a least count of 0.01 mm.

Question 1

What is meant by base and derived quantities? Give the names and symbols of SI base units.

Accepted Answer

Base quantities Base quantities: The independent physical quantities on which all other quantities are built. They cannot be described in terms of any other quantity. Scientists chose seven base quantities. Length, mass and time are the three we meet most often in this book. Derived quantities Derived quantities: Quantities that are described by multiplying or dividing base quantities. Examples: speed = distance ÷ time; area = length × breadth; density = mass ÷ volume. Their units (m s⁻¹, m², kg m⁻³) are called derived units. The seven SI base quantities and units Length, metre, m; Mass, kilogram, kg; Time, second, s; Electric current, ampere, A; Temperature, kelvin, K; Amount of substance, mole, mol; Luminous intensity (brightness of light), candela, cd Every other quantity in physics, from force to electric charge, can be built from these seven.

Question 2

Give three examples of derived units in SI. How are they derived from base units?

Accepted Answer

What a derived unit is A derived unit is the unit of a derived quantity. It is obtained by multiplying or dividing the SI base units in the same way the quantity itself is defined. Three examples Area, length × breadth, m × m, square metre (m²); Volume, length × breadth × height, m × m × m, cubic metre (m³); Speed, distance ÷ time, m ÷ s, metre per second (m s⁻¹) A unit with its own name Force = mass × acceleration. Unit = kg × m s⁻² = kg m s⁻². This combination is given the special name newton (N).  Derived units come only from multiplying or dividing base units, never from adding or subtracting them.

Question 3

State the similarities and differences between Vernier Callipers and a micrometer screw gauge.

Accepted Answer

Similarities Both measure small lengths more precisely than a metre rule.; Both have a main scale and a second, finer scale.; Both can have a zero error, which must be found and corrected before use.; Both give the reading as: main scale reading + (lined-up division × least count). Differences Least count, 0.1 mm (0.01 cm), 0.01 mm (0.001 cm); Precision, Less precise, 10 times more precise; Second scale, Sliding vernier scale, Rotating circular scale on the thimble; Holds the object with, Jaws, Anvil and spindle; Can measure, Outer size, inner size and depth, Only outer size (thickness, diameter); Range (about), Up to about 15 cm, Up to about 2.5 cm; Typical use, Diameter of a pipe, depth of a beaker, Diameter of a wire, thickness of a sheet Choose the Vernier Callipers for something a few millimetres to a few centimetres across, and the screw gauge for something less than a millimetre thick.

Question 4

Identify and explain the reasons for human errors, random errors and systematic errors in experiments.

Accepted Answer

What an error is An error is the difference between a measured value and the true value. Every measurement has some error; the aim is to make it as small as possible. 1. Human errors These are mistakes made by the person taking the measurement. Reading a scale at an angle (parallax error).; Writing down a wrong value or unit.; Slow reaction when starting or stopping a stopwatch. Take care and repeat each reading.; Keep the eye at right angles to the scale.; Use digital or automatic instruments where possible. 2. Systematic errors These push every reading off by the same amount in the same direction, so repeating the reading does not help. Zero error in the instrument.; Poor calibration or wrong markings on the scale.; A fault in the way the apparatus is set up. Check the zero before measuring and correct for it.; Compare the instrument with a more accurate one.; Apply a correction factor to the readings. 3. Random errors These make repeated readings of the same quantity come out slightly different each time, in no fixed pattern. Small changes in temperature, air currents or voltage.; Small differences in how each reading is taken. Take many readings and find their average.; Time many swings of a pendulum (say 20) and divide, instead of timing one. Readings: 11.0 cm, 11.1 cm, 11.2 cm. Average = (11.0 + 11.1 + 11.2) ÷ 3 = 33.3 ÷ 3. 11.1 cm Human, Careless or misread values, Care, repetition, digital instruments; Systematic, All readings off the same way, Check and correct the instrument; Random, Readings scatter, Average many readings

Question 5

Differentiate between precision and accuracy of a measurement with examples.

Accepted Answer

Precision Precision: How close repeated measurements of the same quantity are to each other. Precision depends on the instrument: the smaller its least count, the more precise the reading. A screw gauge (0.01 mm) is more precise than a metre rule (1 mm). Accuracy Accuracy: How close a measurement is to the true (accepted) value. Accuracy depends on careful work, a correctly calibrated instrument with no zero error, and recording enough significant figures. Examples 99.9, 100.1, 100.2, 90, Precise (close together) but not accurate (far from the true value); 98, 101, 102, 100, Accurate (close to the true value) but less precise (spread out); 99.9, 100.1, 100.2, 100, Both precise and accurate A clock that is always exactly 5 minutes fast is precise (steady) but not accurate (wrong). Conclusion Precision is about consistency; accuracy is about correctness. A good measurement needs both.

Question 6

What is measurement? Explain why we need standard units.

Accepted Answer

Definition Measurement: The process of comparing an unknown quantity with a known, fixed standard quantity called a unit. The two parts of a measurement 5 m, 5, metre; 250 g, 250, gram; 30 s, 30, second A measurement without a unit is meaningless: "the rod is 5 long" could mean 5 mm or 5 km. Problems with early measurements Long ago people measured with hand spans, arm lengths (cubits) and footsteps. Since every person's hand, arm and foot are different, the same object gave different measurements, which caused confusion in trade and building. Need for standard units A standard unit means the same thing to everyone, everywhere.; Anyone measuring the same object gets the same result.; Trade is fair: a kilogram of sugar is the same in every shop.; Scientists in different countries can compare and share their results. This is why the world uses the International System of Units (SI), with seven base units fixed by international agreement.

Question 7

What are prefixes? Explain their use in measurement with examples.

Accepted Answer

Definition Prefix: A word or symbol placed before a unit to multiply it by a power of ten. Why prefixes are used Very large and very small quantities are long and awkward to write. Writing 50 000 000 m or 0.000 04 m is slow and easy to get wrong. Prefixes make such values short and easy to read. 50 000 000 m, 50 Mm (megametres); 5000 m, 5 km (kilometres); 0.001 m, 1 mm (millimetre); 0.000 004 s, 4 µs (microseconds) Common prefixes giga, G, 10⁹; mega, M, 10⁶; kilo, k, 10³; centi, c, 10⁻²; milli, m, 10⁻³; micro, µ, 10⁻⁶; nano, n, 10⁻⁹ Examples of use A millimetre (one thousandth of a metre) is handy for the thickness of a coin or a wire.; A kilometre (one thousand metres) is handy for the distance between cities.; A megawatt describes the output of a power station. Capital and small letters matter: m = milli, M = mega.

Question 8

What is scientific notation? Explain with examples.

Accepted Answer

Definition Scientific notation (standard form): A short way of writing a very large or very small number as N × 10ⁿ, where N is from 1 up to (but not including) 10 and n is a whole number. N × 10ⁿ,  1 ≤ N < 10 Why it is used Long strings of zeros take space, are hard to read and compare, and lead to mistakes in calculations. Powers of ten keep numbers short and make their size clear at a glance. How to write a number in scientific notation Move the decimal point until only one non-zero digit is left before it.; Count the number of places you moved it: that is n.; Moved to the left (a big number): n is positive. Moved to the right (a small number): n is negative. Examples Distance from the Earth to the Sun, about 150 000 000 km, 1.5 × 10⁸ km; Speed of light, 300 000 000 m s⁻¹, 3.0 × 10⁸ m s⁻¹; Radius of a hydrogen atom, about 0.000 000 000 053 m, 5.3 × 10⁻¹¹ m; Thickness of a sheet of paper, 0.0001 m, 1 × 10⁻⁴ m Scientific notation also shows the significant figures clearly: 5.00 × 10³ has three, 5 × 10³ has one.

Question 9

Write a note on the metre rule. How is parallax error avoided?

Accepted Answer

The metre rule A metre rule is a scale one metre long, marked in centimetres and millimetres. It is used in the laboratory to measure lengths such as the length of a table, a book or a rod. Least count of a metre rule: 1 mm (0.1 cm): the smallest length it can measure correctly. How to measure a length Place the rule along the object, touching it.; Line up the zero mark with one end of the object.; Read the mark at the other end with your eye directly above it.; The reading at the other end is the length. Parallax error If the scale is read from the side, the mark appears to shift and the object seems longer or shorter than it is. This is parallax error. Keep the eye directly above the mark, at right angles to the scale.; Keep the object touching the scale, or stand the rule on its edge so the marks touch the object. If the end of the rule is worn

Question 10

Describe the construction and working of Vernier Callipers.

Accepted Answer

Introduction Vernier Callipers measure small lengths precisely, to 0.1 mm (0.01 cm): the diameter of a pipe or a coin, the inner size of a test tube, or the depth of a beaker. Construction Main scale: fixed, marked in millimetres.; Vernier scale: slides along the main scale; it is 9 mm long and divided into 10 equal divisions.; Outside jaws: one fixed, one sliding; they grip an object to measure its outer size.; Inside jaws: on the top; they fit inside an object to measure its inner size.; Depth rod (tail): slides out of the end to measure depth.; Lock screw: holds the vernier in place while you read it. Least count 1 main scale division = 1 mm, and 10 vernier divisions = 9 mm, so 1 vernier division = 0.9 mm. LC = 1 MSD − 1 VSD = 1 mm − 0.9 mm = 0.1 mm = 0.01 cm Working: taking a reading Close the jaws and check for zero error.; Hold the object gently between the outside jaws.; Main scale reading (MSR): read the main scale mark just before the vernier's zero.; Vernier reading: find the vernier line (n) that lines up exactly with a main scale line.; Reading = MSR + (n × LC); then correct for any zero error. Reading = 2.3 cm + (7 × 0.01 cm). 2.37 cm Zero error and its correction No zero error, The two zeros line up exactly, 0; Positive, Vernier zero is to the right of the main zero, + (n × LC); Negative, Vernier zero is to the left of the main zero, − (10 − n) × LC Corrected reading = observed reading − zero error Digital Vernier Callipers show the reading on a screen and have a least count of 0.01 mm.

Question 11

Describe the construction and working of a micrometer screw gauge.

Accepted Answer

Introduction A micrometer screw gauge measures very small lengths, to 0.01 mm: the diameter of a thin wire or the thickness of a thin sheet. Construction U-shaped frame that holds the other parts.; Anvil: fixed stud at one end; the object is placed against it.; Spindle: moves towards the anvil when the thimble is turned.; Sleeve: carries the main scale and a horizontal datum line.; Thimble: carries the circular scale, usually 50 or 100 divisions.; Ratchet: turns the thimble and slips (clicks) once the object is gripped, so it is never squeezed too hard. Pitch and least count Pitch: The distance the spindle moves in one complete turn of the thimble, for example 0.5 mm or 1 mm. LC = pitch ÷ number of circular scale divisions Working: taking a reading Close the gauge and check for zero error.; Place the object between the anvil and spindle; turn the ratchet until it clicks.; Main scale reading (MSR): the last mark visible on the sleeve.; Circular scale reading (CSR): the thimble line that meets the datum line.; Reading = MSR + (CSR × LC); then correct for any zero error. Reading = 3 mm + (70 × 0.01 mm). 3.70 mm Zero error On the datum line, No zero error, None; Below the datum line, Positive (reads too much), Subtract it; Above the datum line, Negative (reads too little), Add its size Always use the ratchet, not the thimble, for the final turn; otherwise you squeeze the object and get a wrong reading.

Question 12

Write a note on the physical balance. How is it used?

Accepted Answer

What it is A physical balance is a sensitive beam balance used in the laboratory to measure the mass of an object. It works on the principle of a lever: the beam balances when the masses on the two pans are equal. Mass and weight In daily life we say "weight" for mass, but in physics they differ: mass is the quantity of matter (kg), while weight is the force of gravity on it (N), measured with a spring balance. A balance compares masses, so it gives the same reading anywhere. Steps for using it Level the base: turn the levelling screws until the plumb line hangs exactly over its mark.; Check the beam: raise the beam with the knob; the pointer should rest at zero. If not, adjust the balancing screws.; Place the object on the left pan.; Add standard masses to the right pan with forceps, never with fingers.; Balance it: adjust the masses until the pointer stays at zero, or swings equally either side of it.; Read the mass: the total of the standard masses on the right pan is the mass of the object. Lower the beam before adding or removing anything from the pans, so the knife-edges are not damaged.

Question 13

Write a note on the stopwatch.

Accepted Answer

What it is A stopwatch measures the time taken by an event, for example the time for a pendulum to swing or for a runner to finish a race. Mechanical stopwatch It has two hands: one for seconds and one for minutes. The dial is divided into 30 big divisions, each split into 10 small divisions, so one small division is 0.1 s: its least count. Digital stopwatch It shows the time as numbers on a screen and usually reads to 0.01 s, so it is more precise. Works by, Spring and gears, Electronic circuit; Display, Hands on a dial, Numbers on a screen; Least count, 0.1 s, 0.01 s; Power, Wound by hand, Battery How to use it Press the knob (button) to start the watch as the event begins.; Press it again to stop it when the event ends.; Note the reading, then press once more to reset to zero. Human reaction time (about 0.2 s) limits any hand-operated stopwatch, so time several repeats and take the average.

Question 14

Describe the measuring cylinder. How is the volume of an irregular solid found with a measuring cylinder and a displacement can?

Accepted Answer

Measuring cylinder A measuring cylinder is a tall glass or transparent plastic cylinder marked in millilitres (mL) or cubic centimetres (cm³). It measures the volume of liquids, and of solids that do not dissolve. 1 mL = 1 cm³. Reading the meniscus Place the cylinder on a level surface and bring your eye level with the liquid surface. Water curves down (concave), so read the bottom of the curve; mercury curves up (convex), so read the top. Method 1: measuring cylinder Pour water into the cylinder and note the level: V₁ = 50 mL. Tie the stone with a thread and lower it gently into the water; note the new level: V₂ = 75 mL. Volume of stone = V₂ − V₁ = 75 − 50. 25 mL = 25 cm³ Method 2: displacement can (for a large solid) Place the displacement can on a level table.; Fill it with water until water starts flowing out of the spout; wait until it stops.; Place an empty measuring cylinder under the spout.; Lower the solid, tied with a thread, gently into the can.; The solid pushes out (displaces) its own volume of water into the cylinder.; Read the volume of the collected water: this is the volume of the solid.

Question 15

Explain the concept of uncertainty in measurement.

Accepted Answer

No measurement is perfect Except for counting, every measurement has some uncertainty: a range within which the true value lies. One big cause is the instrument itself, which can only read to its smallest division. Uncertainty and least count Suppose the end of a line lies between the 10.3 cm and 10.4 cm marks of a metre rule. We record the nearer mark: If the end has not reached halfway between the marks, record the lower mark (10.3 cm).; If it has reached or passed halfway, record the higher mark (10.4 cm). Either way, the true length could be up to half a division away from what we wrote: the uncertainty is about ± 0.05 cm, half the least count. Many books simply quote it as ± one least count (± 0.1 cm) to be safe. Length read on a metre rule: 10.3 cm. Least count = 0.1 cm. 10.3 ± 0.1 cm Uncertainty and significant figures Significant figures show uncertainty too: 10.3 cm (3 significant figures) means the last digit, 3, is the doubtful one. A more precise instrument lets us record more significant figures. A smaller least count means a smaller uncertainty.

Question 16

What are significant figures? Explain the rules for counting them with examples.

Accepted Answer

Definition Significant figures: In a measurement, all the accurately known digits plus the first doubtful digit. A rod's end lies between the 4.6 cm and 4.7 cm marks. One student writes 4.6 cm, another 4.7 cm: both agree on the 4; the second digit is estimated. So the measurement has 2 significant figures: one certain digit and one doubtful digit.  Rules All non-zero digits are significant, 5.67 m, 3; Zeros between non-zero digits are significant, 5.06 m, 3; Leading zeros (before the first non-zero digit) are not significant, 0.0034 m, 2; Trailing zeros after a decimal point are significant, 2.40 mm, 3; In scientific notation, all digits before × 10ⁿ are significant, 3.50 × 10⁻⁴ m, 3 Significant figures in calculations Add or subtract, Keep the fewest decimal places, 12.321 − 10.3 = 2.0; Multiply or divide, Keep the fewest significant figures, 2.5 × 1.23 = 3.1 A zero like the one in 5000 is unclear; write 5 × 10³ or 5.00 × 10³ to show exactly how many figures are significant.

Question 17

Explain the rules for rounding off numbers in scientific measurements.

Accepted Answer

Why we round off A calculation often gives more digits than the measurements justify. We round the answer to the right number of significant figures so it does not claim more precision than we have. Rules If the digit after the last one kept is less than 5, leave the last kept digit unchanged.; If it is more than 5, increase the last kept digit by 1.; If it is exactly 5: increase the last kept digit if it is odd, and leave it if it is even. Examples 2.512 × 10³ m, 2 significant figures, 2.5 × 10³ m, Next digit 1 is less than 5; 3.4567 × 10⁴ kg, 3 significant figures, 3.46 × 10⁴ kg, Next digit 6 is more than 5; 4.45 × 10² m, 2 significant figures, 4.4 × 10² m, Exactly 5, and 4 is even; 4.55 × 10² m, 2 significant figures, 4.6 × 10² m, Exactly 5, and 5 is odd Some teachers always round 5 upward. Ask which rule your examiner uses, and use it every time.

Base quantity	SI base unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Electric current	ampere	A
Temperature	kelvin	K
Amount of substance	mole	mol
Luminous intensity (brightness of light)	candela	cd

Derived quantity	Definition	How the unit is derived	Derived unit
Area	length × breadth	m × m	square metre (m²)
Volume	length × breadth × height	m × m × m	cubic metre (m³)
Speed	distance ÷ time	m ÷ s	metre per second (m s⁻¹)

Point	Vernier Callipers	Micrometer screw gauge
Least count	0.1 mm (0.01 cm)	0.01 mm (0.001 cm)
Precision	Less precise	10 times more precise
Second scale	Sliding vernier scale	Rotating circular scale on the thimble
Holds the object with	Jaws	Anvil and spindle
Can measure	Outer size, inner size and depth	Only outer size (thickness, diameter)
Range (about)	Up to about 15 cm	Up to about 2.5 cm
Typical use	Diameter of a pipe, depth of a beaker	Diameter of a wire, thickness of a sheet

Type	Effect	Main cure
Human	Careless or misread values	Care, repetition, digital instruments
Systematic	All readings off the same way	Check and correct the instrument
Random	Readings scatter	Average many readings

Readings	True value	Result
99.9, 100.1, 100.2	90	Precise (close together) but not accurate (far from the true value)
98, 101, 102	100	Accurate (close to the true value) but less precise (spread out)
99.9, 100.1, 100.2	100	Both precise and accurate

Without a prefix	With a prefix
50 000 000 m	50 Mm (megametres)
5000 m	5 km (kilometres)
0.001 m	1 mm (millimetre)
0.000 004 s	4 µs (microseconds)

Prefix	Symbol	Value
giga	G	10⁹
mega	M	10⁶
kilo	k	10³
centi	c	10⁻²
milli	m	10⁻³
micro	µ	10⁻⁶
nano	n	10⁻⁹

Quantity	Ordinary form	Scientific notation
Distance from the Earth to the Sun	about 150 000 000 km	1.5 × 10⁸ km
Speed of light	300 000 000 m s⁻¹	3.0 × 10⁸ m s⁻¹
Radius of a hydrogen atom	about 0.000 000 000 053 m	5.3 × 10⁻¹¹ m
Thickness of a sheet of paper	0.0001 m	1 × 10⁻⁴ m

Case	What you see with the jaws closed	Zero error
No zero error	The two zeros line up exactly	0
Positive	Vernier zero is to the right of the main zero	+ (n × LC)
Negative	Vernier zero is to the left of the main zero	− (10 − n) × LC

Circular zero, with the gauge closed	Type	Correction
On the datum line	No zero error	None
Below the datum line	Positive (reads too much)	Subtract it
Above the datum line	Negative (reads too little)	Add its size

	Mechanical	Digital
Works by	Spring and gears	Electronic circuit
Display	Hands on a dial	Numbers on a screen
Least count	0.1 s	0.01 s
Power	Wound by hand	Battery

Rule	Example	Significant figures
All non-zero digits are significant	5.67 m	3
Zeros between non-zero digits are significant	5.06 m	3
Leading zeros (before the first non-zero digit) are not significant	0.0034 m	2
Trailing zeros after a decimal point are significant	2.40 mm	3
In scientific notation, all digits before × 10ⁿ are significant	3.50 × 10⁻⁴ m	3

Operation	Rule	Example
Add or subtract	Keep the fewest decimal places	12.321 − 10.3 = 2.0
Multiply or divide	Keep the fewest significant figures	2.5 × 1.23 = 3.1

Number	Round to	Result	Reason
2.512 × 10³ m	2 significant figures	2.5 × 10³ m	Next digit 1 is less than 5
3.4567 × 10⁴ kg	3 significant figures	3.46 × 10⁴ kg	Next digit 6 is more than 5
4.45 × 10² m	2 significant figures	4.4 × 10² m	Exactly 5, and 4 is even
4.55 × 10² m	2 significant figures	4.6 × 10² m	Exactly 5, and 5 is odd

Long Questions with Answers

Set A: Textbook comprehensive questions 5 questions

What is meant by base and derived quantities? Give the names and symbols of SI base units.

Base quantities

Derived quantities

The seven SI base quantities and units

Give three examples of derived units in SI. How are they derived from base units?

What a derived unit is

Three examples

A unit with its own name

State the similarities and differences between Vernier Callipers and a micrometer screw gauge.

Similarities

Differences

Identify and explain the reasons for human errors, random errors and systematic errors in experiments.

What an error is

1. Human errors

2. Systematic errors

3. Random errors

Differentiate between precision and accuracy of a measurement with examples.

Precision

Accuracy

Examples

Conclusion

Set B: More important long questions 12 questions

What is measurement? Explain why we need standard units.

Definition

The two parts of a measurement

Problems with early measurements

Need for standard units

What are prefixes? Explain their use in measurement with examples.

Definition

Why prefixes are used

Common prefixes

Examples of use

What is scientific notation? Explain with examples.

Definition

Why it is used

How to write a number in scientific notation

Examples

Write a note on the metre rule. How is parallax error avoided?

The metre rule

How to measure a length

Parallax error

If the end of the rule is worn

Describe the construction and working of Vernier Callipers.

Introduction

Construction

Least count

Working: taking a reading

Zero error and its correction

Describe the construction and working of a micrometer screw gauge.

Introduction

Construction

Pitch and least count

Working: taking a reading

Zero error

Write a note on the physical balance. How is it used?

What it is

Mass and weight

Steps for using it

Write a note on the stopwatch.

What it is

Mechanical stopwatch

Digital stopwatch

How to use it

Describe the measuring cylinder. How is the volume of an irregular solid found with a measuring cylinder and a displacement can?

Measuring cylinder

Reading the meniscus

Method 1: measuring cylinder

Method 2: displacement can (for a large solid)

Explain the concept of uncertainty in measurement.

No measurement is perfect

Uncertainty and least count

Uncertainty and significant figures

What are significant figures? Explain the rules for counting them with examples.

Definition

Rules

Significant figures in calculations

Explain the rules for rounding off numbers in scientific measurements.

Why we round off