SI Units and Conversions

Unit Conversions and measurements calculations are fundamental requirements to solve any problem of Physics. What would happen if there were no units? Can you imagine? Physics will get converted into Mathematics by becoming the study of all physical quantities only by numbers and nothing else. People in the past used to measure they walked by counting the number of steps it took them to travel or complete that distance. So, it is obvious that the measurement was never accurate, and each physical quantity was measured only by numbers. Hence, it was the need of that time to introduce some kind of identity that could make measurements more accurate and easily understandable. In this article, you’ll understand what are units, what are different types of units, different units systems followed around the globe.

What Are Units And Physical Quantities?

Units are basic standards that are essential if we want to express or compare any physical quantity in physical terms. A physical quantity is a largely used term, especially in the field of science. Physical Quantities in science are of two types: Derived Quantities & Underived Quantities(Fundamental Quantities). 

To understand how units and physical quantities are linked to each other and work cordially together let’s take one scenario where there is one race, the length of the race track is the physical quantity, and how we measure this physical quantity i.e. length is called a unit. So, as we already know, we generally measure the distance or length of any track in meters or kilometers generally. 

But, here comes a problem, not every unit like meter, inches, or miles can be made an international standards unit that could be used everywhere. A good unit is that which is easily available, independent of any external physical factors like space, and universally accepted.

Later in this article, we will read about the International System Of Units (SI Units) which will clear things up with more details on each unit.

Types Of Units

Fundamental Units: – Units that are used to measure and represent fundamental physical quantities are called fundamental units. 

For example, 

• Second is used to represent the time.
• Meter is used to represent the length.
• Kilograms are used to represent the weight or mass.
• Coulomb is used to represent the amount of charge.
• Kelvin is used to represent temperature.
• Mole is used to represent the quantity of chemical substance.
• Candela is used to represent the intensity of light.

Derived Units: – Units that are used to measure and represent derived physical quantities are called Derived Units. All other derived quantities can be defined by some scientific use of fundamental units easily. The unit of current Ampere could easily be found out by dividing the charge flown upon time i.e. Charge/Time, (C/sec)

Different Systems Of Units

There are several systems introduced by various physicists and scientists from all over the globe, but there are broadly two systems of measuring units. 

One is the International System of Units (SI units) and the other widely used measurement system is the English System introduced by Britishers and is still popularly used in some cities of the United States. 

SI Units (International System Of Units)

The SI Units (International System Of Units) was introduced to avoid all sorts of confusion in various regions and nations in deciding the final standard set of rules and units that will be accepted universally everywhere. 

The SI units were implemented and initiated by the BPIM (Bureau International des Poids and Mesures), which is a French organization that presented measurement standards in various fields like science.

SI units are only introduced to assist in giving scientific definitions to a few physical quantities and that are fundamental underived physical quantities because if they could add a definite unit that will accept every standard, it will make calculations hell easier. 

Metric Prefix Conversion

Metric Prefix Conversion deals with changing the level of measurements to a higher range from any lower standard. This sounds complicated. Don’t worry!

We know that if we have to measure the length of the racing track, we should use “meter” the SI unit for length to measure it, but what will you do if you have to measure the distance of the Earth from the Sun, or distance of Pluto from the Sun. You’ll realize that the “meter” unit we use to measure the length of the racing track is not suitable to measure such long distances.

Here comes the role of metric conversions. We can convert meters into kilometers which is also a unit used to measure distance especially, large distances as we discussed in the example.

Length

1 meter = 1/1000000000 gigameters = 1/1000000 megameters = 1/1000 kilometers = 10 decimeter = 100 centimeters = 1000 millimeters = 1000000 micrometers = 10000000000 nanometers.

Time

1 year = 365 days

1 day = 24 hours

1 hour = 60 minutes

1 minute = 60 seconds

1 second = 1000 milliseconds

Mass

1 gram = 1/1000000000 gigagrams = 1/1000000 megagrams = 1/1000 kilograms = 10 decigrams = 100 centigrams = 1000 milligrams = 1000000 micrograms = 10000000000 nanograms.

1 metric tonne = 1000 kilograms

Force

1 Newton = 10000 dyne

1 Newton = 0.102 Kgf

1 Newton = 0.225 Pound-Force

Conversions within the units to measure the same physical quantity may look like a very tiring task but it helps a lot to speed up the calculations and accuracy if you’re solving difficult problems based on unit conversion. You should try to remember these different prefixes and practice them to master them. 

Conclusion

Units are broadly divided into systems standard one is SI units and the other one is English units. The SI unit is widely accepted and broadly spread to every corner of the world. BPIM, the regulatory body for standardizing measurement units across the globe introduced the International System Of Units which only focused on providing international level units to the seven fundamental physical quantities. We also learned how we can convert a single unit to measure largely differentiated physical quantities.