Units of measurement are things made by humans to help us measure things, and thus be able to communicate consistently. There is fundamental amount of mass or distance, although the second, the base unit of time in the International System of Units is 1 /86400 of a day. Which is twenty four hour days, divided by one sixteith for minutes, divided by sixty equal unis for seconds of the time it takes the earth to rotate once. Check?

The international system of units is also called the metric system. It’s built on seven units:

Quantity name symbol

time (second) (s)

length (length) (m)

mass (kilogram) (kg)

electric current (ampere) (A)

temperature (kelvin) (K)

amount of substance (mole) (mol)

luminious intensity (candela) (cd)

Many other concepts are derived from these units of measurement. As an example:

Speed is length divided by time (speed = metres / seconds)
Acceleration is length divided by time also (acceleration = metres / seconds squared)
Force is acceleration multiplied by mass (Force = mass x acceleration)
Work is force multipled by distance (work = force x distance)
Power is work divided by time (Power = Work / Time)

Units can be divided into exact numbers, and measured numbers. Measured numbers normally exist to shorten the decimal places in exact numbers of the sake of speed of communication.

Scientific notation, and significant figures help tell us
In addition and multiplication we use the same number of significant figures in the least precises figure.hank green