Video Lesson

Lesson Objective

Dear Learners,

At the end of this section, you should be able to:

• Classify physical quantities as fundamental and derived physical quantities;
• Describe derived physical quantities in terms of fundamental quantities;
• Differentiate between fundamental and derived units;
• Classify physical quantities as scalar and vector quantities.

Brainstorming Question

What is the difference between fundamental and derived physical quantities? Some physical quantities have only magnitude. However, other physical quantities have both magnitude and direction. Can you mention some examples of these physical quantities?

key terms and concepts

Physical Quantity

A physical quantity is anything that you can measure. For example, length, temperature, distance and time are physical quantities.

Physical quantities are classified based on their nature and how they can be measured. This classification helps in understanding, measuring, and expressing various physical phenomena. The primary categories are:

1. Fundamental (Base) Quantities: are the basic physical quantities that are defined independently and cannot be described in terms of other quantities. They form the foundation of physical measurements.

Examples:

• Length (meter), mass (kilogram), time (second), electric current (ampere), temperature (kelvin), amount of substance (mole), luminous intensity (candela).

2. Derived Quantities: are those that are formed by combining fundamental quantities through mathematical relationships. They are dependent on the fundamental quantities.

Examples:

• Velocity (meters per second), acceleration (meters per second squared), force (newton), energy (joule), power (watt), pressure (pascal).

Physical quantities can also be classified as scalar and vector quantities. These are:

1. Scalar Quantities: are defined by only their magnitude and do not have a direction. They are fully described by a numerical value and a unit.

Examples: Temperature, mass, time, distance, speed, etc.

2. Vector Quantities: are defined by both their magnitude and direction. They require both a numerical value and a direction to be fully described.

Examples: Displacement, velocity, acceleration, force, momentum, etc.