Chapter 1: Physical Quantities and MeasurementsMCQs with Answers
All 24 MCQs of 9th Class Physics Chapter 1, Physical Quantities and Measurements, with answers and the reason each option is right or wrong: the 11 textbook exercise MCQs plus 13 more board-style MCQs. Punjab Board new syllabus.
Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
A note about the questions
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
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Set A: Textbook exercise 11 MCQs
The multiple-choice questions at the end of Chapter 1 in your book, in the book's option order.
Q1.1Vernier Callipers and Screw Gauge
The instrument that is most suitable for measuring the thickness of a few sheets of cardboard is:
Answer(c) Vernier Callipers
Step by step
Estimate the size first: a few sheets of cardboard together are only a few millimetres thick.
A thickness of a few millimetres needs a reading finer than 1 mm, so we want a least count of about 0.1 mm.
Vernier Callipers read to 0.1 mm, and their jaws can hold the sheets without crushing them.
Why the others are wrong
(a) a metre rule reads only to 1 mm, too rough for something this thin.
(b) a measuring tape also reads only to 1 mm.
(d) the screw gauge is for very thin, hard objects such as wire; its spindle presses into soft cardboard. For one sheet of paper it would be the right choice.
Remember
Metre rule 1 mm, Vernier 0.1 mm, screw gauge 0.01 mm: pick the coarsest one that is still fine enough.
Q1.2Prefixes and Scientific Notation
One femtometre is equal to:
Answer(b) 10⁻¹⁵ m
Step by step
The prefix femto (symbol f) means 10⁻¹⁵.
So 1 femtometre = 1 fm = 1 × 10⁻¹⁵ m.
Why the others are wrong
(a) 10⁻⁹ m is a nanometre.
(c) 10⁹ m would be a gigametre.
(d) 10¹⁵ m would be a petametre, which is huge.
Remember
Small prefixes in steps of 10⁻³: milli, micro, nano, pico, femto, atto.
Q1.3Prefixes and Scientific Notation
A light year is a unit of:
Answer(c) distance
Step by step
Do not be fooled by the word "year": a light year is the distance light travels in one year.
Distance = speed × time = (3 × 10⁸ m s⁻¹) × (about 3.15 × 10⁷ s).
So 1 light year is about 9.46 × 10¹⁵ m. Astronomers use it because stars are extremely far away.
Why the others are wrong
(a) light is not a quantity with this unit.
(b) this is the trap: a year is time, but a light year is not.
(d) speed needs a unit such as m s⁻¹.
Remember
Light YEAR sounds like time, but it measures how FAR.
Q1.4Physical Quantities and SI Units
Which one is a non-physical quantity?
Answer(c) colour
Step by step
A physical quantity can be measured with an instrument and written as a number with a unit.
Distance (m), density (kg m⁻³) and temperature (K) all pass this test.
Colour, as we see it, depends on the person looking at it, so it is treated as non-physical.
Why the others are wrong
(a) distance is measured in metres.
(b) density is measured in kg m⁻³.
(d) temperature is measured in kelvin.
Remember
No instrument and no unit means non-physical.
Q1.5Measuring Volume
When using a measuring cylinder, one precaution to take is to:
Answer(d) position the eye in line with the bottom of the meniscus
Step by step
Water curves at its surface. This curved surface is called the meniscus.
The correct reading is at the bottom of this curve.
If the eye is above or below that level, the reading is wrong (parallax error), so keep your eye level with the bottom of the meniscus.
Why the others are wrong
(a) a measuring cylinder has no moving zero to check.
(b) looking from below causes the very error we are avoiding.
(c) looking from different angles adds errors instead of removing them.
Remember
Eye level, bottom of the curve (top of the curve for mercury).
Q1.6Measuring Volume
Volume of water consumed by you per day is estimated in:
Answer(b) litre
Step by step
A person drinks roughly 2 to 3 litres of water a day.
The litre gives a small, easy number, so it is the sensible unit.
Why the others are wrong
(a) millilitres are too small: you would get thousands of mL.
(c) the kilogram is a unit of mass, not volume.
(d) a cubic metre is 1000 litres, far too large.
Remember
Pick the unit that gives a small, easy number.
Q1.7Measuring Volume
A displacement can is used to measure:
Answer(d) volume of a solid
Step by step
The can is filled with water up to its spout.
When a solid is lowered in, it pushes water out through the spout.
The volume of water that comes out equals the volume of the solid, even for an irregular solid such as a stone.
Why the others are wrong
(a) mass is measured with a balance.
(b) mass is measured with a balance.
(c) the volume of a liquid is read directly from a measuring cylinder.
Remember
Displacement can: the water pushed out equals the solid put in.
Q1.8Significant Figures
Two rods with lengths 12.321 cm and 10.3 cm are placed side by side. The difference in their lengths is:
Answer(b) 2.0 cm
Step by step
Subtract: 12.321 − 10.3 = 2.021 cm.
When adding or subtracting, the answer keeps only as many decimal places as the least exact number.
12.321 has 3 decimal places and 10.3 has only 1, so the answer gets 1 decimal place.
Round 2.021 to 1 decimal place: 2.0 cm. The zero stays, because it shows the precision.
Why the others are wrong
(a) 2.02 cm has too many decimal places.
(c) 2 cm has no decimal place, so it hides the precision of the measurement.
Four students measure the diameter of a cylinder with Vernier Callipers. Which of the following readings is correct?
Answer(c) 3.47 cm
Step by step
The least count of Vernier Callipers is 0.01 cm.
So a correct reading must show exactly 2 decimal places when written in cm.
Only 3.47 cm has 2 decimal places.
Why the others are wrong
(a) 3.4 cm has only 1 decimal place, what a metre rule gives.
(b) 3.475 cm has 3 decimal places, finer than the instrument can read.
(d) 3.5 cm has only 1 decimal place.
Remember
A reading shows as many decimal places as the least count.
Q1.10Prefixes and Scientific Notation
Which of the following measures is likely to represent the thickness of a sheet of this book?
Answer(b) 1 × 10⁻⁴ m
Step by step
Use common sense first: a sheet of paper is about a tenth of a millimetre thick.
Convert: 0.1 mm = 0.1 × 10⁻³ m = 1 × 10⁻⁴ m.
Check: 500 sheets are about 5 cm (0.05 m) thick, and 0.05 ÷ 500 = 1 × 10⁻⁴ m.
Why the others are wrong
(a) 6 × 10⁻²⁵ m is far smaller than an atom; no paper is that thin.
(c) 1.2 × 10⁻¹⁵ m is the size of a nucleus.
(d) 4 × 10⁻² m is 4 cm, the thickness of a whole thick book.
Remember
Estimate in mm first, then convert to metres.
Q1.11Vernier Callipers and Screw Gauge
In a Vernier Callipers, ten smallest divisions of the Vernier scale are equal to nine smallest divisions of the main scale. If the smallest division of the main scale is half a millimetre, the Vernier constant is equal to:
Answer(c) 0.05 mm
Step by step
Given: 1 main scale division (MSD) = 0.5 mm, and 10 VSD = 9 MSD.
One vernier division: 1 VSD = 9 × 0.5 mm ÷ 10 = 0.45 mm.
Vernier constant = 1 MSD − 1 VSD = 0.5 mm − 0.45 mm = 0.05 mm.
Short way: 1 MSD ÷ number of vernier divisions = 0.5 ÷ 10 = 0.05 mm.
Why the others are wrong
(a) 0.5 mm is just the main scale division.
(b) 0.1 mm is the answer when 1 MSD = 1 mm; here the MSD is half of that.
(d) 0.001 mm does not come from these numbers.
Remember
Vernier constant = smallest main-scale division ÷ number of vernier divisions.
Set B: More MCQs from this chapter 13 MCQs
Extra questions on the same ideas, of the kind set in board papers and class tests.
QB1Physical Quantities and SI Units
Which one of the following units is not a derived unit?
Answer(b) kilogram
Step by step
The seven base units are metre, kilogram, second, ampere, kelvin, mole and candela.
Kilogram is on that list, so it is a base unit, not a derived one.
Why the others are wrong
(a) the pascal is N m⁻², built from base units.
(c) the newton is kg m s⁻², built from base units.
(d) the watt is J s⁻¹, built from base units.
Remember
Seven base units: m, kg, s, A, K, mol, cd.
QB2Physical Quantities and SI Units
Amount of a substance in terms of numbers is measured in:
Answer(d) mole
Step by step
"In terms of numbers" means counting particles such as atoms or molecules.
The SI unit for counting particles is the mole; one mole has about 6.02 × 10²³ particles.
Why the others are wrong
(a) the gram is a unit of mass.
(b) the kilogram is a unit of mass.
(c) the newton is a unit of force.
Remember
Counting particles means the mole.
QB3Significant Figures
The number of significant figures in 0.00650 s is:
Answer(b) 3
Step by step
Zeros at the start only hold the place of the decimal point, so 0.00 does not count.
Count from the first non-zero digit: 6, 5, 0.
A zero at the end, after a decimal point, does count, so there are 3 significant figures.
Why the others are wrong
(a) 2 forgets the last zero.
(c) 5 wrongly counts zeros at the start.
(d) 6 wrongly counts every zero.
Remember
Leading zeros never count; trailing zeros after a decimal point always do.
QB4Significant Figures
Which of the following numbers shows 4 significant digits?
Answer(d) 0.001248
Step by step
9000.8 has 5: zeros between non-zero digits count.
4 has only 1.
5174.00 has 6: zeros at the end after a decimal point count.
0.001248 has 4: the zeros at the start do not count, leaving 1, 2, 4, 8.
Why the others are wrong
(a) 9000.8 has 5 significant digits (some answer keys wrongly mark it).
(b) 4 has 1 significant digit.
(c) 5174.00 has 6 significant digits.
Remember
Count each option; do not trust a key that marks 9000.8.
QB5Prefixes and Scientific Notation
Which of the following prefixes represents the largest value?
Answer(c) peta
Step by step
Write each as a power of ten: mega = 10⁶, pico = 10⁻¹², peta = 10¹⁵, kilo = 10³.
The biggest power is 15, so peta is the largest.
Why the others are wrong
(a) mega (10⁶) is large but much smaller than peta.
(b) pico (10⁻¹²) is extremely small.
(d) kilo is only 10³.
Remember
Large prefixes in steps of 10³: kilo, mega, giga, tera, peta, exa.
QB6Vernier Callipers and Screw Gauge
A micrometer can be used to measure:
Answer(c) length
Step by step
A micrometer is another name for the micrometer screw gauge.
It measures small lengths such as the diameter of a wire.
Why the others are wrong
(a) current is measured with an ammeter.
(b) force is measured with a spring balance.
(d) mass is measured with a balance.
Remember
Screw gauge = thin wire = length.
QB7Vernier Callipers and Screw Gauge
The instrument that best measures the internal diameter of a pipe is:
Answer(b) Vernier Callipers
Step by step
"Internal" means the inside of the pipe, so the instrument must fit inside it.
Vernier Callipers have special inside jaws for this job.
Why the others are wrong
(a) a screw gauge measures outside sizes only.
(c) a metre rule cannot grip the inside and is not fine enough.
(d) a tape cannot grip the inside and is not fine enough.
Remember
Inside jaws for inner size, depth rod for depth.
QB8Vernier Callipers and Screw Gauge
The least count of a screw gauge is 0.01 mm. If the main scale reading is zero and the third line of its circular scale coincides with the datum line, the measurement is:
Answer(c) 0.03 mm
Step by step
Reading = main scale reading + (circular scale reading × least count).
Put in the values: 0 + (3 × 0.01 mm).
Reading = 0.03 mm.
Why the others are wrong
(a) 0 mm ignores the circular scale.
(b) 3 mm forgets to multiply by the least count.
(d) 0.3 mm uses 0.1 mm as the least count.
Remember
Always multiply the circular-scale line by the least count.
QB9Prefixes and Scientific Notation
9.483 × 10³ m is the standard form of:
Answer(d) 9483 m
Step by step
10³ means 1000, so multiply: 9.483 × 1000.
Move the decimal point 3 places to the right: 9483 m.
Why the others are wrong
(a) 94.83 m moves the point only 1 place.
(b) 9.483 m does not move the point at all.
(c) 948.3 m moves the point only 2 places.
Remember
Positive power: move the point right that many places.
QB10Physical Quantities and SI Units
Which of the following is a base unit?
Answer(d) mole
Step by step
Check against the list of seven base units: metre, kilogram, second, ampere, kelvin, mole, candela.
Mole is on it.
Why the others are wrong
(a) the pascal (pressure) is a derived unit.
(b) the coulomb (charge) is a derived unit, A s.
(c) metre per second (speed) is a derived unit.
Remember
Seven base units: m, kg, s, A, K, mol, cd.
QB11Significant Figures
The number having one significant digit is:
Answer(d) 6 × 10²
Step by step
In scientific notation, only the digits before the × sign count; the 10² part does not.
6 × 10² has just one digit, 6, so it has 1 significant digit.
Why the others are wrong
(a) 1.1 has 2 significant digits.
(b) 6.0 has 2, because a zero at the end after a decimal point counts.
(c) 7.1 has 2 significant digits.
Remember
Ignore the power of ten when counting significant figures.
QB12Prefixes and Scientific Notation
The ratio of millimetre to micrometre is:
Answer(c) 1000
Step by step
Write both in metres: 1 mm = 10⁻³ m and 1 µm = 10⁻⁶ m.
Ratio = 10⁻³ m ÷ 10⁻⁶ m = 10⁻³⁻⁽⁻⁶⁾ = 10³ = 1000.
The metres cancel, so the ratio has no unit.
Why the others are wrong
(a) a ratio of like quantities has no unit.
(b) it has a unit and is upside down.
(d) 0.001 is the ratio turned upside down.
Remember
A ratio of two lengths is just a number.
QB13Prefixes and Scientific Notation
0.2 mm in units of metres is:
Answer(c) both (a) and (b)
Step by step
1 mm = 10⁻³ m, so 0.2 mm = 0.2 × 10⁻³ m.
As a decimal: 0.2 × 0.001 = 0.0002 m.
In scientific notation: 2 × 10⁻⁴ m. These are the same number, so both are right.
Why the others are wrong
(a) the value is right, but picking only (a) leaves out (b), which is the same number.
(b) the value is right, but picking only (b) leaves out (a), which is the same number.
(d) (a) and (b) are both correct. Some tests misprint (b) as 2 × 10⁴ m; the power must be negative.
Remember
Check every option before choosing; two can be the same value.
