In The Real Life, Seller and Buyer, trading process will be hard if results of measuring made by seller and buyer are not same. Therefore, seller always weights using a scale. His or her good is compered to a certain unit of measurement agreed all over the world. Specific measuring tool is used to measure quantity such as weight. What are benefits of measurement in humans life? What should we learn in measuring?
When your going to traditional market, you wear your shoes. What is the size of your shoes? Do you have same size with your friends or other people? Why Not? What time do you go to traditional market everyday? How long do you take to go to traditional market? How far is it from your home to the traditional market?
Unconsciously, all of the activities you do related to the science you are going to learn, in other to know the sixe of shoes, time to travel, and the distance from the house to the market, we need measurement. What is measurement? What tools do you need in measurement? Why? However, before you can measure and using corect mesurement tools, you need to understand the definition of quantity and unit.
Before I explain about quantities and units, then I invite you to do simple activities. Measure length of your desk with a ballpoint. In turns out that the result is eight times of the ballpoint's length. From the result of the mesurement, we can write the length of the desk=8 ballpoints. Then, measure the length of the desk using palm ribs. It turn out that the result is three time the rib's length. Thus, the result can written as the desk length = 3 palm leaf ribs. Measure the desk using other tools and write the results. And write in the comments the results and what tools you used to measure!
From the activity, it can be concluded that to measure means an activity of comparing things. Something to compared is called quantity, while the one to compare is called unit. The number accompanies the unit is called as the result of the mesurement. In the activity you have done, length is the quantity and ballpoint and ribs are the units. Thus, quantity is something that can be measured and has units. Unit is anything serves to compere in a quantity. Thus, quantity and unit are related into each other.
In Physics quantity is differentiated into two, basic quantity and derivative quantity. Based on the value and direction, quantity is classified into scalar quantity and vector quantity. However, now you can learn besic quantity and derivative quantity and their units, when you study physics.
A. Basic Quantity and its Units
Base Quantity or Basic Quantity is the base to make other quantity. In Conference Generate des Poids et Measure (CGPM) 1960, scientist agreed to generalize unit system known System International (SI). In the conference, 7 basic quantity were decided. You can see the sevent quantities and their units on the table.
Beside those seven quantities, there are also other quantities decided in the conference. The quantities are flat angle and room angle. Unit for flat angle is radian (rad), while unit for room angle is steradian (Sr).
B. Derivative Quantity
Derivative quantity is quantity whose unit comes from two or more basic quantities, you can see derivative quantity in the table.
