Key Terms

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Last edited 26 days ago by Learn LoopHQ.

Chapter: 03. Physical Quantities And Measurement 2

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Time: The interval between two events.

Mean solar day: The time taken by the Earth to complete one rotation about its own axis.

Second (s): The standard unit of time in the SI system.

Minute (min): A bigger unit of time, equal to 60 seconds.

Hour (h): A bigger unit of time, equal to 60 minutes or 3600 seconds.

12-hour clock: A time convention where the day is divided into two 12-hour periods (a.m. and p.m.).

a.m. (ante meridiem): Means ‘before midday’, used for times from midnight to just before noon.

p.m. (post meridiem): Means ‘after midday’, used for times from noon to just before midnight.

24-hour clock: A time convention that records time from 0000 to 2400 hours without using a.m. or p.m.

Sundial: An instrument that measures time by the position of the shadow cast by the sun.

Water clock: An early instrument used to measure time by regulating the flow of water.

Candle clock: An early instrument that measures time by the burning of a marked candle.

Sand clock: An early instrument, also known as an hourglass, that measures time by the flow of sand through a narrow opening.

Pendulum clock: A clock that measures time using a swinging weight, or pendulum.

Stopwatch: An instrument used to record the precise time interval that has lapsed between two events.

Atomic clock: The most precise time-measuring device that measures time according to the vibrations within atoms.

Temperature: The degree of hotness or coldness of a body.

Kelvin (K): The standard unit of temperature in the SI system.

Degree Celsius (°C): A commonly used unit of temperature.

Degree Fahrenheit (°F): A commonly used unit of temperature.

Thermometer: An instrument used to measure temperature.

Laboratory thermometer: A thermometer used to measure room temperature or the temperature of solids and liquids in a laboratory.

Capillary tube: A very fine glass tube with a very small bore, found inside thermometers.

Stem: The thick glass tube that protects the capillary tube of a thermometer and has graduations marked on it.

Constriction: A slight bend or kink in the capillary tube of a clinical thermometer that prevents mercury from falling immediately after removal.

Clinical thermometer: A thermometer used by doctors to measure a person’s body temperature.

Normal body temperature: The average healthy temperature of a person, which is 37° C or 98.6° F.

Digital thermometer: A modern thermometer that uses a sensor to measure temperature and displays it on a digital screen, without using mercury.

Heat: A form of energy that gives the sensation of hotness or coldness of a body.

Joule (J): The SI unit of heat.

Parallax error: An error in reading an instrument that occurs when your eye is not in line with the level of the reading.

Greenwich Mean Time (GMT): The local time at Greenwich, from where the Prime Meridian passes, used as a reference point to measure time across locations.

Rain gauge: A device that collects and measures the amount of rain which falls in a given amount of time per unit area.

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