The second is the basic unit of measurement for time. Because we now have a way to observe time in its smallest unit or form, this was helpful especially in sports and science. Before, 1 second was first used to describe the time spend in the earth’s rotation. Today 1 second is 1/60 of a minute based on the numerical conversion.
The day is divided into 24 hours, each hour divided into 60 minutes, each minute divided into 60 seconds.
A second is 1 / (24 × 60 × 60) of the day. Historically, a day was defined as the mean solar day; i.e., the average time between two successive occurrences of local apparent solar noon.
The meter is used to calculate distance or length. When scientists first thought of the meter, it was described as one ten-millionth of the distance between the equator and the North Pole. Comparing with other metric systems, 1 yard is exactly 0.9144 of a meter.
"The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuumc to be 299792458 when expressed in the unit m s−1, where the second is defined in terms of ∆νCs."[1]
The kilogram is used to compute for mass, which is the measurement of the quantity of matter in any given object. In science the kilogram is used to measure mass, but for us we use it to measure both mass and weight. One kilogram is actually a thousand grams, and although gram can be considered the chief unit, the kilogram (prefix kilo + gram) is used to define measurement for objects with considerable size. In real life, we use the kilogram more to shorten descriptions of measurement that may be too long for comfort (example, 22,000 grams = 22 kilograms).
"The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constanth to be 6.62607015×10−34 when expressed in the unit J s, which is equal to kg m2 s−1, where the metre and the second are defined in terms of c and ∆νCs."[1]
The mass of one litre of water at the temperature of melting ice. A litre is one thousandth of a cubic metre.
Ampere (abbreviated as A). Amperes or more commonly called amps, is used to measure the electric current. Amps can be used to compute for how much electricity runs in a given object, so all conductors of electricity uses amps to
"The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary chargee to be 1.602176634×10−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs."[1]
The original "International Ampere" was defined electrochemically as the current required to deposit 1.118 milligrams of silver per second from a solution of silver nitrate.
The kelvin is used to compute the amount of heat in a certain object. We may be not very familiar with using the kelvin to measure temperature, but it is called the absolute scale because the temperature is only stated in positives (no Kelvin measurement uses the negative sign).
"The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constantk to be 1.380649×10−23 when expressed in the unit J K−1, which is equal to kg m2 s−2 K−1, where the kilogram, metre and second are defined in terms of h, c and ∆νCs."[1]
The Celsius scale: the Kelvin scale uses the degree Celsius for its unit increment, but is a thermodynamic scale (0 K is absolute zero).
To compute for the quantity of substance within an object, SI uses the mole as its basic unit of measurement. Because there are no other available units used to measure the amount of substance within matter, we may also not be aware of using the mole as a unit of measurement, but this is the general term used by scientists
"The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles."[1]
The candela is used to measure the brightness or luminous intensity of an object. You can use this to compute for how much light an object emits, or the amount it glows, or simply how bright it is.
"The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540×1012 Hz, Kcd, to be 683 when expressed in the unit lm W−1, which is equal to cd sr W−1, or cd sr kg−1 m−2 s3, where the kilogram, metre and second are defined in terms of h, c and ∆νCs."[1]
The candlepower, which is based on the light emitted from a burning candle of standard properties.
Mathematically, the dimension of the quantity Q is given by
where a, b, c, d, e, f, g are the dimensional exponents. Other physical quantities could be defined as the base quantities, as long as they form a linearly independentbasis – for instance, one could replace the dimension (I) of electric current of the SI basis with a dimension (Q) of electric charge, since Q = TI.
As examples, the dimension of the physical quantity speedv is
and the dimension of the physical quantity forceF is
