Class 9 Physics Chapter 1 Physical Quantities and Measurement Flashcards

Vocabulary flashcards covering the key terms, definitions, measurement instruments, units, formulas, and error types from Class 9 Physics Chapter 1: Physical Quantities and Measurement.

Physics

The branch of natural science that studies matter, energy, force, motion, space and time, and the relationships between them.

Mechanics

The branch of physics that studies motion, force, and matter.

Heat and Thermodynamics

The branch of physics that studies heat, temperature, and their effects.

Optics

The branch of physics that studies light and its behavior.

Sound

The branch of physics that studies sound and its properties.

Electricity and Magnetism

The branch of physics that studies electric charges, current, circuits, and magnets.

Atomic Physics

The branch of physics that studies atoms and their structure.

Nuclear Physics

The branch of physics that studies atomic nuclei and nuclear processes.

Astronomy

The branch of physics that studies stars, planets, galaxies, and other objects in space.

Physical Quantity

A quantity that can be measured and expressed by a numerical value and a unit.

Non-Physical Quantities

Things that cannot be measured using a physical unit, such as beauty, honesty, happiness, and intelligence.

Base / Fundamental Physical Quantities

Physical quantities that are independent and cannot be expressed in terms of other physical quantities (length, mass, time, electric current, temperature, amount of substance, and luminous intensity).

Derived Physical Quantities

Physical quantities obtained from base quantities by mathematical relationships, such as area, volume, velocity, acceleration, density, and force.

SI System of Units

The International System of Units, which is the internationally accepted system used for measurements to ensure consistency worldwide.

Meter Rule

An instrument used to measure length whose smallest division is usually $1\text{ mm}$ ($0.1\text{ cm}$).

Vernier Calipers

An instrument used to measure small lengths, internal/external diameters, depth, and thickness more accurately than a meter rule.

Least Count

The smallest measurement that an instrument can accurately measure.

Zero Error

An error that occurs when the zero mark of an instrument's measuring scale (such as the Vernier scale) does not coincide correctly with the zero mark of the main scale when closed.

Screw Gauge

An instrument used to measure very small lengths, such as the diameter of a thin wire or thickness of a sheet, with higher precision than a Vernier caliper.

Pitch

The distance moved by the screw of a screw gauge during one complete rotation.

Physical Balance

An instrument commonly used in laboratories to measure the mass of an object based on the principle of moments.

Stopwatch

An instrument used in experiments to measure a time interval.

Human Reaction Time

A small error that occurs when a person manually starts or stops a stopwatch, producing a random error in measurement.

Volume

The amount of space occupied by an object or substance, with the SI unit of $\text{m}^3$.

Displacement Method

A technique used to find the volume of an irregular solid by placing it into water in a measuring cylinder and calculating $\text{Final volume} - \text{Initial volume}$.

Density

The amount of mass contained in a given volume of a substance, given by the formula $\rho = \frac{m}{V}$.

Mass

The amount of matter in an object, which does not change when the object is moved from one place to another; its SI unit is kilogram ($\text{kg}$).

Weight

The force with which a gravitational field attracts an object, calculated as $W = mg$ with the SI unit of newton ($\text{N}$).

Prefixes

Factors used with units to represent very large or very small quantities (e.g., kilo = $10^3$, milli = $10^{-3}$, micro = $10^{-6}$).

Scientific Notation

A convenient way to write very large or very small numbers in the form $a \times 10^n$, where $1 \text{ ≤ } a < 10$.

Significant Figures

Digits that show the precision of a measurement, including all accurately known digits and the first doubtful or estimated digit.

Accuracy

A description of how close a measured value is to the true or accepted value.

Precision

A description of how close repeated measurements are to one another.

Systematic Error

An error that occurs in a consistent way and affects measurements in the same direction, often caused by zero error or incorrect calibration.

Random Error

An error that varies from one measurement to another, caused by factors like human reaction time or small changes in experimental conditions.

Personal / Human Error

Errors caused by the observer or person taking the measurement, such as reading a scale from the wrong angle.

Parallax Error

An error in measurement that occurs when a scale is viewed from an incorrect angle.