Question

Fill in the blanks with the correct words:
_______ (kilometer/Cubit) is a non-standard unit of length.

Answer 1

Hint: We know that both the given units are that of the length. But normally, we call the measurements under the SI units ‘standard’. First look at how we define each of the given units and then determine which could be called the standard unit among them.

Complete step-by-step answer:
Cubit is a unit used for measuring length since the ancient and medieval period. If we were to define one cubit, it could be defined as the length of the arm from elbow to the tip of the middle finger (average of 18 inches). Clearly, this measurement varies from person to person. Hence, we cannot consider cubit as a standard unit.
Since, measurement is inevitable in every field of science and also in our day to day life. Hence, there is a need to universalize these measurements of different commodities. That is where the international system of units (abbreviated as SI) comes into picture. It is based on seven base units or fundamental units along with which we have the scope of unlimited number of additional units (derived units) and also we have prefixes that represent powers of ten. So, these SI units are what we call the standard units. SI unit of length is meter and kilo is the prefix that represents${{10}^{3}}$.
Hence, kilometer is definitely a standard unit of length.
So, we could conclude that Cubit is the nonstandard unit of length among the given two.
Hence, the answer to the question is Cubit.

Additional information:
The fundamental or base quantities are,
Meter – length
Seconds – time
Mole-amount of substance
Ampere-electric current
Kilogram-mass
Kelvin-temperature
Candela- luminous intensity
Some of the prefixes used with these units are,
${{10}^{-3}}$ -milli, ${{10}^{-2}}$ -centi, ${{10}^{3}}$ -kilo,${{10}^{-6}}$ -micro,${{10}^{-9}}$ -nano , etc.

Note: The word standard in this question refers to units under the modern metric system which is otherwise called International System of Units (SI). Units under this category often come with prefixes like milli, centi, giga, nano, etc. This system has almost replaced all the other measurement systems of olden times. However, the United Kingdom, Canada and other countries formerly part of the British Empire still use the imperial system of units.