Physical Quantities and Measurements is the first chapter of Class 9 Physics. In this chapter, students learn how scientists measure different physical quantities such as length, mass, time, and temperature.
Measurement is very important in physics because every scientific experiment depends on accurate measurements. This chapter also introduces students to the SI system of units, prefixes, scientific notation, and important measuring instruments.
Understanding these basic concepts will make it easier for students to study the next chapters of physics.
Topics Included in This Chapter
The following important topics are explained in these notes:
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Physical Quantities
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Base Quantities and Base Units
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Derived Quantities
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International System of Units (SI Units)
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Prefixes used in measurements
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Scientific Notation
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Significant Figures
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Measuring Instruments
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Metre Rule
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Vernier Calipers
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Micrometer Screw Gauge
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Measurement of Time
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Measurement of Mass
These topics help students understand how measurements are made and used in physics.
MCQs – Class 9 Physics Chapter 1
1. Which one is a non-physical quantity?
(a) Distance
(b) Density
(c) Colour
(d) Temperature
✅ Answer: (c) Colour
2. Which of the following can be measured by an instrument?
(a) Fear
(b) Affection
(c) Time
(d) Wisdom
✅ Answer: (c) Time
3. What does SI stand for?
(a) Standard Input
(b) Systematic International
(c) Scientific Integration
(d) International System
✅ Answer: (d) International System
4. What is the SI derived unit for area?
(a) m
(b) m²
(c) m³
(d) m/s
✅ Answer: (b) m²
5. What is the scientific notation for 0.00004 m?
(a) 4 × 10⁴
(b) 4 × 10⁻⁵
(c) 0.4 × 10⁻³
(d) 40 × 10⁻⁶
Answer: (b) 4 × 10⁻⁵ ✅
6. The surface of water in a container is:
(a) Convex
(b) Flat
(c) Concave
(d) None of these
Answer: (b) Flat ✅
7. Which type of error is caused by personal mistakes or limitations such as poor observation or reaction time?
(a) Systematic error
(b) Random error
(c) Human error
(d) Instrumental error
Answer: (c) Human error ✅
8. Which of the following is NOT a cause of systematic errors?
(a) Zero error of instrument
(b) Poor calibration
(c) Environmental fluctuations
(d) Incorrect markings on the instrument
Answer: (c) Environmental fluctuations ✅
Short Questions – Class 9 Physics Chapter 1
1. What is measurement? Name its two parts.
Answer:
Measurement is the process of comparing a physical quantity with a standard unit of the same kind to determine its value.
Two parts of measurement:
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Magnitude (numerical value): The number that shows how many units of measurement are present.
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Unit: The standard quantity used to measure a physical quantity (e.g., metre for length, second for time).
Example:
If the length of a table is 2 metres, then:
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Magnitude = 2
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Unit = metre (m)
2. What is the difference between a physical quantity and a non-physical quantity?
Answer:
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Physical Quantity:
A physical quantity is something that can be measured and expressed with a numerical value and a unit.
Example: Length, mass, time, temperature. -
Non-Physical Quantity:
A non-physical quantity cannot be measured directly and does not have standard units.
Example: Love, beauty, fear, wisdom.
3. What are the SI units of length, mass, and time?
Answer:
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Length: metre (m)
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Mass: kilogram (kg)
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Time: second (s)
4. How do you write a number in scientific notation?
Answer:
To write a number in scientific notation:
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Move the decimal point so that only one non-zero digit remains on the left.
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Multiply the number by 10 raised to the power of the number of places the decimal has moved.
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If the decimal moves to the left, the exponent is positive.
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If the decimal moves to the right, the exponent is negative.
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Example:
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0.0005 = 5 × 10⁻⁴
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4500 = 4.5 × 10³
Why These Notes Are Useful
These notes are prepared to help students understand the chapter easily and prepare for exams.
In these notes you will find:
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Clear and simple explanations
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Important definitions
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MCQs for practice
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Short questions
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Long questions
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Exercise solutions
The content is organized in a way that makes learning and revision easier for students.
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