Definitions [23]
Define mass.
The quantity of matter contained in a body is known as its mass.
Mass is the measure of the amount of matter in an object.
State or define the following term:
An hour
It is defined as 1/24 the part of the mean solar day.
State or define the following term:
Mean solar day
The average of the varying solar days, when the earth completes one revolution around the sun, is called mean solar day.
Define Standard metre.
The standard metre is defined in terms of the speed of light, according to which one metre is the distance travelled by light in `1/(299,792,458)` of a second in the air (or vacuum).
State or define the following term:
Minute
It is defined as the 1/1440 part of the mean solar day.
State or define the following term:
Year
One year is defined as the time in which earth completes one complete revolution around the sun.
Define measurement.
Measurement is the process of comparison of the given physical quantity with the known standard quantity of the same nature.
Define standard meter.
A standard metreis equal to 1650763.73 wavelengths in vacuum, of the radiation from krypton isotope of mass 86.
Define a fundamental quantity.
The physical quantities like mass, length and time which do not depend on each other are known as fundamental quantities.
State or define the following term:
Solar day
The time taken by the earth to complete one rotation about its own axis is called solar day.
State or define the following term:
Second
“A second is defined as 1/86400 the part of a mean solar day.”
OR
Second may also be defined “as to be equal to the duration of9,192,631,770 vibrations corresponding to the transition between two hyperfine levels of cesium – 133 atoms in the ground state.”
A set of particular physical quantities from which different other units can be obtained, which are neither derived from one another nor resolved into any other units is called fundamental units.
Define mass Mention its unit.
Mass is the amount of matter contained in a body. Its unit is a kilogram (kg).
Define the term density of a substance.
The density of a substance is defined as the mass of a unit volume of that substance.
`"Density" = "Mass"/"Volume"`
Define one metre, the S.I. unit of length. State it's one multiple and one submultiple.
One metre is defined as the distance travelled by light in the air in `1/(299,792,458)` of a second.
The S. I. unit of length is meter.
Multiple of metre = Kilometre (km).
Submultiple of metre = Centimetre (cm)
A value, quantity, or magnitude in terms of which other values, quantities, or magnitudes are expressed is called a unit.
The smallest value up to which an instrument can measure is called the least count.
Units that are neither fundamental nor derived but are accepted in the SI system (e.g., radian for plane angle, steradian for solid angle) is called supplementary units.
Units that are derived from fundamental units — such as force, which is mass × acceleration — and are expressed algebraically using base units is called derived units.
The basic physical quantities that cannot be derived from other quantities and serve as the foundation for all measurements is called fundamental quantities.
The quantities that are derived from fundamental quantities through mathematical relationships is called derived quantities.
A quantity that can be measured by an instrument and through which we describe the laws of the physical world is called a physical quantity.
Define the term volume of an object.
The space occupied by an object is called its volume.
Formulae [1]
Least count = \[\frac {\text {Smallest reading on main scale}}{\text {No. of divisions on main scale}}\]
Instrument Least Count = \[\frac {\text {Main scale least count}}{\text {Divisions on secondary scale}}\]
