Measurement and Physical Quantities

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Questions and Answers

What is the main purpose of measurement?

To compare an unknown quantity to a known one (correct)

To classify physical quantities into two types

To analyze data without numerical values

To determine the size of an object without units

Which of the following is considered a fundamental quantity?

Speed

Volume

Temperature (correct)

Density

Which unit corresponds to a derived quantity?

Cubic meter (m³) (correct)

Second (s)

Meter (m)

Kilogram (kg)

What is the SI unit of length?

Meter (m) Signup and view all the answers

Which statement correctly defines derived quantities?

Quantities that can be expressed in terms of fundamental quantities. Signup and view all the answers

Which of the following measurements would likely require a weighing scale?

Finding the weight of a bag of flour Signup and view all the answers

What system was adopted in 1960 for standard units of measurement?

SI (Système international d'unités) system Signup and view all the answers

What is a light year used to measure?

Distance traveled by light in one year Signup and view all the answers

What is the primary purpose of an odometer?

To calculate distance in kilometers between two places Signup and view all the answers

Which of the following is equivalent to 1 parsec?

3.26 light years Signup and view all the answers

What SI unit is used for measuring mass?

Kilogram Signup and view all the answers

Which instrument is used for precise measurement of mass?

Electronic balance Signup and view all the answers

How is weight defined?

The force of gravity on an object Signup and view all the answers

What is a characteristic of atomic clocks?

They use periodic vibrations within an atom for accuracy Signup and view all the answers

What is the SI unit of temperature?

Kelvin Signup and view all the answers

Which type of clock is considered more accurate than a mechanical clock?

Quartz clock Signup and view all the answers

What is the SI unit of electric current?

Ampere Signup and view all the answers

Which formula represents the relationship between electric current, charge, and time?

I = Q/T Signup and view all the answers

What is the measure of the number of entities in a substance called?

Amount of substance Signup and view all the answers

Which of the following describes the SI unit of luminous intensity?

Candela Signup and view all the answers

What is a radian in terms of angle measurement?

The angle subtended at the center of a circle by an arc whose length equals the radius Signup and view all the answers

What does accuracy in measurement refer to?

Closeness of a measured value to the correct value Signup and view all the answers

What is the process of rounding off in measurements aimed to achieve?

To obtain a value that is acceptably close to the exact measurement Signup and view all the answers

What is Avogadro's number used to express?

The number of particles in a mole Signup and view all the answers

Study Notes

Measurement

Measurement is the comparison of a known quantity to an unknown one.
Measuring is the act of determining the magnitude of a quantity.
Examples of everyday measurements include using measuring tapes (length), stopwatches (time), and weighing scales (mass).

Physical Quantities

Physical quantities are measurable quantities.
They are expressed with a numerical value and a unit.

Fundamental Quantities

Fundamental quantities cannot be expressed in terms of other physical quantities.
Examples include mass, length, time, and temperature.

Derived Quantities

Derived quantities can be expressed in terms of fundamental quantities.
Examples include area, volume, density, speed, and solid angle.

Units

A unit is a standard quantity used to compare unknown quantities.
Units for fundamental quantities are called fundamental units (e.g., second, kilogram).
Units for derived quantities are called derived units (e.g., square meter, cubic meter).

SI System

The International System of Units (SI) is a system based on meter, kilogram, second, ampere, kelvin, and candela.

Fundamental Quantities: Length

Length is the extent between two points.
SI: meter (m).
Light year: Distance light travels in one year (9.46 × 10¹⁵ m). Used for astronomical distances.
Odometer: Device measuring distance.
Parsec: A unit of distance used in astronomy (1 parsec = 3.26 light-years).
Astronomical Unit (AU): Average distance from Earth to Sun (1.496 × 10¹¹ m).
Fermi (f): Unit used in nuclear physics.

Fundamental Quantities: Mass

Mass is the amount of matter in a body.
SI: kilogram (kg).
Atomic mass unit (amu): (1/12)th the mass of a ¹²C atom. Used for measuring subatomic particles.
Larger weights are measured in tonnes (1 tonne = 1000 kg).

Weight

Weight is the force of gravity acting on an object.
Calculated as weight = mass × acceleration due to gravity.
Weight's SI unit is newton (N).

Measuring Equipment: Mass

Beam balance: Compares an unknown mass to a known mass.
Electronic balance: Provides precise measurements.

Fundamental Quantities: Time

Time is the duration of events and intervals between them.
SI: second (s).
Larger units: days, months, years.
Mechanical, quartz, and atomic clocks are used for measuring time.

Fundamental Quantities: Temperature

Temperature is a measure of hotness or coldness.
SI: kelvin (K), also measured in Celsius (°C) and Fahrenheit (°F).
0 K = -273°C (absolute zero).
Thermometers: Used for measuring temperature.

Fundamental Quantities: Electric Current

Electric current is the flow of electric charges.
SI: ampere (A).
Measured with ammeters.
Current = Charge/time.

Fundamental Quantities: Amount of Substance

Amount of substance is the number of entities in a substance.
SI: mole (mol).
Mole contains 6.02 × 10²³ entities (Avogadro's number).

Fundamental Quantities: Luminous Intensity

Luminous intensity is the power of a light source.
SI: candela (cd).
Measured by photometers.

Supplementary Quantities: Plane Angle

Plane angle is the angle made by two intersecting lines.
SI: radian (rad).

Supplementary Quantities: Solid Angle

Solid angle is formed by planes intersecting at a point.
SI: steradian (sr).

Derived Quantities: Area

Area is the space occupied by a 2D shape.
Measured in square units (e.g., m²).

Derived Quantities: Volume

Volume is the space occupied by a 3D object.
Measured in cubic units (e.g., m³).

Derived Quantities: Density

Density is mass per unit volume.
Density = mass/volume.
SI: kg/m³.

Accuracy In Measurement

Errors are uncertainties in measurements.
Accuracy: Closeness to the true value.
Precision: Closeness of repeated measurements to each other.
Approximation: Finding a number close to the exact value.
Rounding off: Adjusting the number of digits in a measurement.

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Description

This quiz covers the concepts of measurement, physical quantities, fundamental and derived quantities. It explores the definitions and units associated with these quantities, providing a strong foundation in understanding how measurements function in everyday life.