Basic and Derived Units|Units and dimensions #Engineeringphysics#units #dimensions

Summary

This lecture covers the fundamentals of physical units and dimensions, emphasizing their importance in engineering. It introduces various systems of units like CGS, FPS, and MKS, with a focus on the SI (International System of Units), which is widely used in science and engineering. The lecture explains the seven basic quantities and their corresponding units, such as mass (kg), length (m), and time (s). It also covers derived units, including area, volume, velocity, and pressure, formed by combining base units. Additionally, it highlights rules for writing units correctly to avoid errors in measurements.

Takeaways

• 😀 Units express the value and similarity of quantities, providing them with dimension and face value.
• 😀 A unit of a physical quantity is a randomly chosen standard, widely accepted for measuring similar quantities.
• 😀 Every measurement consists of two parts: a number and a unit (e.g., 30 meters).
• 😀 The major systems of units include CGS, FPS, MKS, MKSA, and the British system, but the SI system is most commonly used in science and engineering.
• 😀 SI (International System of Units) is the standard system used globally, comprising seven basic units for fundamental quantities.
• 😀 The seven basic SI units are: kilogram (kg) for mass, meter (m) for length, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, candela (cd) for luminous intensity, and mole (mol) for amount of substance.
• 😀 Basic units are independent of other units and serve as the foundation for all other measurements.
• 😀 Supplementary units include the radian for measuring angles and the steradian for measuring solid angles.
• 😀 When writing units, avoid using plural forms, punctuation marks, and always use agreed symbols for clarity.
• 😀 Derived units are combinations of two or more base units, such as area (m²), volume (m³), velocity (m/s), and pressure (N/m²).

Q & A

What is the primary purpose of using units in measurements?

Units are used to express the value and similarities of quantities, providing them with a dimension and a face value. They standardize measurements, ensuring clarity and consistency across different fields.

Why is it important to include units when working with quantities in engineering?

In engineering, it's crucial to include units alongside the numbers when expressing quantities. Omitting units could lead to errors or incorrect interpretations, and your answer might be marked wrong.

What are the basic systems of units mentioned in the script?

The script mentions several systems of units, including the CGS (centimeter, gram, second), FPS (foot, pound, second), MKS (meter, kilogram, second), MKSA (meter, kilogram, second, ampere), and the British system (inches and pounds).

What is the SI unit system, and why is it important?

The SI (International System of Units) is the globally recognized system used in science and engineering. It consists of seven basic units that provide a standardized approach for measurement, making it essential in research and technological fields.

What are the seven basic quantities in the SI unit system?

The seven basic quantities in the SI unit system are mass (kilogram), length (meter), time (second), electric current (ampere), temperature (kelvin), intensity of light (candela), and amount of substance (mole).

How are the SI base units different from supplementary units?

SI base units are fundamental quantities independent of other units, while supplementary units are additional units used for measuring specific quantities like angles (radian) and solid angles (steradian).

What is the rule regarding writing units in plural form?

Units should never be written in their plural form. For example, 'kilogram' should not be written as 'kilograms,' and 'second' should not be written as 'seconds.'

What are derived units, and how are they formed?

Derived units are formed by combining two or more base units. For example, area is derived from length (meter × meter = meter squared), and velocity is derived from length and time (meter/second).

Can you list some examples of derived units mentioned in the script?

Examples of derived units include area (meter squared, m²), volume (meter cubed, m³), velocity (meters per second, m/s), acceleration (meters per second squared, m/s²), density (kilogram per cubic meter, kg/m³), and pressure (newton per square meter, N/m²).

What are some key 'Do's and 'Don'ts' when writing units?

Key 'Do's include using agreed symbols for units and writing them in full. Key 'Don'ts' include using plural forms for units, using punctuation within or at the end of units, and using non-standard abbreviations.