Physics is a branch of science that studies motion, matter, time, and how the universe works. In this branch of science there is material related to measurements that include quantities and units. So the quantity that is determined first is called the basic quantity.
In general, a quantity is anything that can be measured and expressed using numbers and units. In this case, measurements are made using specific measuring instruments where the units used mutually have been agreed upon among scientists long ago.
For example, you measure the length of a house and get a result of 7 meters. The quantity used is “length” using a measuring device in the form of “meters” and the unit is “metres”. Having quantities will make it easier for everyone to measure different things.
Understand the principal amount
Fundamental quantities are defined as fundamental quantities that were previously defined by physicists in ancient times. This quantity is independent and does not depend on other quantities. In fact, it becomes a basis or reference for determining other quantities.
There are 7 types of basic quantities, each with a different symbol and unit. A symbol is a symbol used to write a quantity to make it shorter. This code usually consists of only one or two letters representing that quantity.
Meanwhile, units are a comparison used to express quantity. This comparison was then made in international units (S1) to standardize the measurement results for all people in the world to avoid misunderstanding.
Types of tree sizes
Scientists have identified 7 types of fundamental quantities that apply in general. Starting from length, temperature, electric current, mass, amount of matter, light intensity, and time. To make it easier for you to identify the basic amounts, please see the list in the table below.
| Tree size name | Tree size symbol | lonliness | Unit symbol |
| long | to | meter | M |
| Massa | M | Kg | kg |
| time | W | seconds (seconds) | s |
| Temperature | T | Kelvin | K |
| Strong electric current | I | Ampere | a |
| Light Intensity | I | Candela | CD |
| material quantity | n | Immortal | mall |
1. Long
To measure the length of an object, you will use length. In the International System of Units, the unit of length is the meter (m) with dimensions (L). There are many tools that can be used to measure length, which are rulers, calipers, measuring tapes, and others.
Previously, these quantities and units had been in use since 1960. At that time, scientists showed that 1,650,763.73 times the wavelength of orange-red radiation is the same as the wavelength of a meter. This radiation is emitted into a vacuum by 86 krypton atoms.
Then the unit of the meter was redefined in 1983. Scientists stated that the meter is the length of the path that light travels in a time period of 1/299,792,458 seconds when it is in a vacuum.
Example of using length: Mila has a new pencil that is 22 cm long. To find out the length of the pencil, Mila measured it using a ruler. In this case, cm is not an SI unit, so it can be converted to 0.22 metres.
2. Massa
Mass is defined as the amount of matter present in an object. This quantity has unique properties, which is that its value will remain the same wherever the object is, whether on Earth or in outer space. This is what distinguishes mass from weight.
Most people assume that a body’s mass and weight are the same. But this is incorrect because mass is constant and weight varies. Changes in body weight are affected by the force of gravity acting on the body.
The unit of mass in the International System of Units is the kilogram (kg) with dimensions (m). This quantity can be measured using different types of scales, such as arm scales (two or three arms), electronic or digital scales, and chemical scales to measure small masses.
For example, the mass of Rende’s iron ball is 5 kg. Therefore, even though Rende moved the ball to different places or flew it into space, its mass remained the same. However, if Rende said the weight of the ball is 5 kg, then when it is in space the weight will change.
3 times
The basic quantity used to measure the duration of an event is called time. In the past, this amount was determined based on the Earth’s rotation around its axis, i.e. 1/86,400 hours per day. However, international standards finally use seconds (seconds) as a time unit.
In addition, the dimension of this quantity is T. Many precise instruments used to measure time are clocks, clocks, sundials, stopwatches, and hourglasses. In everyday life, time measurements are usually expressed in hours, minutes, and seconds.
However, if you want to calculate time based on the International System of Units (SI), you must convert it to seconds. For example, my parents’ bike ride to school takes 1 hour, 11 minutes and 1 second. So, the time my parents use is 3,600 seconds + 60 seconds + 1 second = 3,661 seconds.
4. Strong electric current
To measure the electrical charge of an object, you must use a quantity known as electric current. This quantity will count the number of electrons flowing from one point to another. If it reaches the same potential point, the charge stops flowing.
Basically, electric current will travel from objects with high potentials to objects with low potentials. Apart from that, it can also be said that it flows from the positive pole to the negative pole. The unit of this quantity is the ampere (A) in the first dimension.
Instruments that can be used to measure the strength of an electrical current to an object are ammeters, wattmeters, voltmeters, ohmmeters, ammeters, and multimeters. Each tool has a different measurement method, so it must be known and studied first.
5. Temperature
Temperature is defined as the quantity used to determine the high or low temperature of an object. In general, temperature can be expressed in four units, namely Celsius (°C), Kelvin (K), Remor (°R), and Fahrenheit (°F). However, the unit recognized by the SI system is the kelvin (K).
Therefore, if there is a measurement that expresses temperature in other units, it must first be converted to kelvin. The instrument used to measure temperature accurately and correctly is the thermometer, which is also divided into several types.
6. Light intensity
Light intensity is used to calculate whether or not the emitted light reaches the surface of an object. This quantity has international units, the candela (cd), and is expressed in the dimension J.
The instrument used to measure the light intensity of an object is LightMeter or LuxMeter. Among other measuring instruments, this measuring instrument is still relatively common and rarely found and usually only found in laboratories.
7. Quantity of the substance
The last basic quantity is the quantity of matter. This quantity is used to determine the number of molecules or substances present in the body. As is known, every object or object on the face of the Earth consists of certain materials in different quantities and types.
The quantity of a substance expressed in international units is moles with dimension N. Unlike other quantities, the quantity of a substance cannot be measured directly using measuring instruments. To find the quantity, you need to calculate the molar mass of an object.
Example of a tree size question
1. Stefan’s mother bought 15 kg of fine salt to resell at her grocery store. Then the salt is placed in plastic jars with a capacity of 1 liter each. Based on this statement, determine the basic quantity, value, and unit!
Answer:
In Ms. Stefanian’s problem, there are two quantities used, the mass of the fine salt and the volume of the plastic jar. However, the volume of the jar is not specified because it is not a fundamental quantity, and therefore the results for quantities, values and units are obtained as follows.
- Principal amount: mass
- Amount value: 15
- Unit: kilogram (kg)
- The weather in Depok today is very hot with temperature reaching 29 degrees Celsius. Determine the temperature of Depok city using international units applied all over the world?
Answer:
To answer this question, you must first know the formula for converting degrees Celsius to Kelvin, which is:
Temperature (K) = Temperature (°C) + 273.15 K
= 29 + 273.15 k
= 302.15 K
So the temperature of Depok city today in international units is 302.15 K.
2. Nagita wants to know the length of the Japanese pocket book she has. He also measured the pocket book using a ruler. Because the ruler is broken, the starting point for the measurement starts from 5.8 cm to 18.3 cm. Calculate the length of Nagita’s wallet (cm)!
Answer:
To find the actual length of Nagita’s Japanese pocket book, she had to subtract the end point of the measurement from the starting point, as follows:
Pocket book length = final measuring point – initial measuring point
= 18.3 cm – 5.8 cm
= 12.5 cm
Since the question asks for units in centimeters, there is no need to convert to SI.
So, Nagita’s Japanese pocket book is 12.5 cm long.
3. Before going to school, Lala filled her bag with three textbooks of the same size and mass. If the mass of Lala’s bag before it is filled is 23 grams and the final mass is 89 grams, what is the mass of each book in kilograms?
Answer:
Block of 3 books = final block – initial block
= 89 grams – 23 grams
= 66 grams
Since every book has the same mass, then:
Mass of each book =
= 22 grams
= 22 x 0.001 kg
= 0.022 kg
So, the mass of each book in Lala’s bag is 0.022 kg.
4. The temperature in country XYZ is 416 R. Determine the temperature in city XYZ in international units!
Answer:
In SI, temperature has a unit of kelvin, so:
City quarter XYZ = R/0,8 + 273,15 K
= 416/t + 273.15 k
= 520 + 273.15 K
= 793.15 K
So, if the temperature in city XYZ is 416
then in SI it is 793.15 K.
In physics, to know the volume of an object, it must be measured using an instrument that can produce values, quantities, and units. Fundamental quantities were created to serve as a reference in determining different measurement results using the same parameters in the world.