Units of Physical Quantities

Units of Physical Quantities

• Prashant

Physical Quantity

•The quantites which can be measured by an instrument and by means of which we can describe the laws of physics are called physical quantities.

Fundamental Quantitites

By CGPM, certain physical quantities have been chosen arbittrarily and their units are used for expressing all the the other physical quantites

Those chosen physical quantities are known as Fundamental quantites or Base Quantites or Absolute Quantities

Fundamental Quantites

They are independent of each other and cannot be obtained from one another.

The 7 Fundamental Quantities

Fundamental Quantities

• Length

• Mass

• Time

• Thermodynamic Temoperature

• Electric Current

• Amount of Substance

• Luminious Intensity

​In Mechanics Length, Mass and Time are called as Fundamental quantities

Magnitude

Magnitude of physical quantity = (numerical value)

• Magnitude of a physical quantity heavily depends on the selection of UNIT

• •The absolute magnitude of a measurement is independent of the selection on unit.

Magnitude

Units

•Measurement of any physical quantity is expressed in terms of an internationally accepted certain basic reference standard called unit.

•The units for the fundamental or base quantities are called fundamental or base unit. Other physical quantities are expressed as combination of these base units and hence, called derived units

Units

Principle System of Units :

There are various system in use over the world : CGS, FPS, SI (MKS) etc

Units

Units

Multiple Choice

Example of base quantities

• Electric current

• Volume

• Area

• Weight

Multiple Choice

All the following physical quantities are derived quantities except..

• speed

• velocity

• area

• Mass

Multiple Choice

What is the SI unit of weight?

• kilograms

• grams

• newtons

• kg

Multiple Choice

The International System of (SI) unit for temperature is: 

• ℃
• K
• k
• c

Multiple Choice

Which one of these options is NOT a derived quantity?

• Area

• Volume

• Density

• Temperature