International System of Units (SI)
International System of Units (SI)
In our daily lives, many things grow, shrink, or change over time. Every measurable and countable thing that undergoes such changes is referred to as a quantity. Quantities can be classified into various categories based on their field of use and the methods used for their study. These categories include Physical, Mathematical, Chemical, Biological, and more. Physical quantities are essential for understanding and explaining the laws of nature. These quantities enable the mathematical modeling of natural laws. When it comes to mechanics, basic physical quantities like length, mass, and time, along with derived physical quantities, are sufficient to explain this field.
Physical quantities are classified into two main groups based on their appearance and characteristics: scalar quantities and vector quantities.
Scalar quantities are those that are expressed only by a magnitude value. Examples of scalar quantities include mass, temperature, and energy.
Vector quantities, on the other hand, require both magnitude and direction information. Quantities such as force, velocity, and acceleration fall under this category.
These distinctions are extremely important for better understanding the physical world and creating accurate mathematical models.
Imagine you are riding a bicycle on a track, moving at 25 km/h eastward from the starting point. You encounter a turn and need to head north. Even though your speed remains the same (25 km/h), the change in direction creates a new vector velocity.
Later, when you begin to climb a hill, your speed decreases to 15 km/h. However, while going uphill, you are now traveling northeast, so your velocity vector changes direction again. By the end of the race, you might think:
“Throughout the track, my speed and direction changed several times. Sometimes I went directly east, sometimes northwest, and sometimes northeast.”
This type of journey demonstrates how the velocity vector can continuously change and how these changes are connected to the environment.
Measurement Units
Scientists continuously conduct research to better understand fundamental laws and make new discoveries. These studies typically rely on comparing theories with experiments to draw conclusions. Measurements taken during experiments are crucial for ensuring the accuracy and repeatability of the obtained data. In order for the results to be universally understood, it is necessary to establish standard definitions for measurements.
To address this need, the International System of Units (SI) was introduced in 1960. The SI system consists of seven fundamental units that are universally accepted in the fields of science and technology:
In the field of mechanics, typically only the units of mass, time, and length are used. These three fundamental units provide a sufficient foundation for the analysis and study of mechanical systems.
Dimensional Analysis
Dimensional analysis is a powerful method used to examine the relationships between physical quantities in a system. In this analysis, the dimensions of physical quantities are generally defined in terms of basic quantities such as time (T), length (L), and mass (M). The dimensions of other physical quantities are derived from these basic quantities. Dimensional analysis helps us understand how physical quantities interact with one another. For example, the relationship between speed, distance, and time is understood through dimensions, which allows for the formulation of correct solutions.
When constructing physical equations, it is crucial that the dimensions on both sides of the equation are equal. This is essential for the validity of physical laws. For instance, when examining the relationship between force and velocity, it is necessary that the dimensions derived from both sides of the equation match. This equality ensures that the system is modeled correctly and guarantees the reliability of the physical laws.