### Theory:

What is the time now?

Observe the above questions. We might have regularly encountered these questions in our daily life.

These questions refer to quantification of a particular thing. Everything is quantified around us.

The distance we travel is measured in meter or kilometer, the vegetables we buy are measured in gram or kilogram, the time we follow is measured in minutes and hours.

But what are these quantities?

These quantities are known as physical quantities.

Physical quantities:
The physical quantities are used to measure any process or the properties of any substances.
Example:
1. The change in weather can be measured in the temperature.

2. The weight of an object is measured in gram or kilogram.
Now we understand about physical quantities, but have you ever wondered why we use different physical quantities?

The purpose of using different physical quantities:

To differentiate the measurements based on its properties, we use different physical quantities.

For example, we cannot measure the distance between the two points and the temperature of a place using the same physical quantities. Because these two are different measurements.

And that's why we are using different quantities for different measurements.

The physical quantities can be classified into two types:

1. Fundamental quantities.

2. Derived quantities.

Fundamental quantities:
• The fundamental quantities are a basic requirement in physical measurements.
• The fundamental quantities are used to derive all other quantities.
Example:
1. Time

2. Length

3. Mass

Derived quantities:

In measurements to avoid using many fundamental quantities, the derived quantities are introduced.

The derived quantities are combined from the fundamental quantities, and using relations in the measurements.
Quantities like area, volume, and density can be expressed in terms of other fundamental quantities. They are called derived quantities.
Example:
We used to calculate the area of a place, which is the derived quantity because the area is related to the fundamental quantity of length.

Now we understand the physical quantities and it's various types, but how do you measure physical quantities? Do you have any idea?

Keep thinking!! We'll see that in an upcoming lesson.