By Info4all Physical Quantity:
 |
| Physical Quantity |
All the measurable quantity are called physical quantity.
OR
It is the property of a body, that can be measure or calculate from other measurements.
For example:
we define distance and time by specifying methods for measuring them, whereas we define average speed by stating that it is calculated as distance traveled divided by time of travel.
Measurements of physical quantities are expressed in terms of units, which are standardized values. For example, the length of a race, which is a physical quantity, can be expressed in units of meters (for sprinters) or kilometers (for distance runners). Without standardized units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way.
Types of Physical Quantity.
- Base Physical Quantity (Base Quantity)
- Drive Physical Quantity (Drive Quantity)
Base Physical Quantity (Base Quantity)
The physical quantity on the basis of which other quantity are form are called base quantity or fundamental quantity.
These are :
- Length
- Mass
- Time
- Electric Current
- meter (m)
- kilogram (kg)
- second (s)
- ampere (A)
Drive Physical Quantity (Drive Quantity)
The physical quantities which are formed by base quantities.
OR
The physical quantities which are formed by multiplying or dividing base quantities are called base physical quantities.
For example:
- Area
- Velocity
- Acceleration
- Momentum
- Distance
- Displacement
- Speed
- Power
- P.E
- K.E
SI ( System International) Units .
A standard set for measurements.
SI units play a vital role in scientific and technological research and development.
Type of SI Units
- Base Units
- Drive Units
Base Units:
The seven basic unit on the basis of which other drive unit are form, are called base quantity or fundamental quantity.
These are :
|
S NO |
Name of Units |
SI Units |
SI Units Symbol |
|
1 |
Length |
Meter |
m |
|
2 |
Mass |
Kilogram |
kg |
|
3 |
Time |
Second |
s |
|
4 |
Electric Current |
Ampere |
A |
|
5 |
Temperature |
Kalvin |
K |
|
6 |
Amount of Substance |
Mole |
mol |
|
7 |
Luminous Intensity |
Candela |
cd |
- Unit of length, meter (m): Meter is the SI unit of length and is defined by taking the fixed value of the speed of light in vacuum. It is expressed as m.s-1.
- Unit of mass, kilogram (kg): Kilogram is the SI unit of mass and is defined by taking the fixed value of the Planck constant. It is expressed as kg.m2.s-1.
- Unit of time, second (s): Second is the SI unit of time and is defined by taking the fixed value of Cesium frequency. It is expressed as s1.
- Unit of electric current, ampere (A): Ampere is the SI unit of electric current and is defined by taking the fixed value of the elementary charge.
- Unit of thermodynamic temperature, Kelvin (K): Kelvin is the SI unit of thermodynamic temperature and is defined by taking the fixed value of Boltzmann constant k = 1.380649×10-23.
- Unit of the amount of substance, mole (mol): Mole is the SI unit of the amount of substance and is defined by the fixed value of Avogadro constant NA. One mole contains 6.02214076×1023 elementary entities and is expressed as mol-1.
- Unit of luminous intensity, candela (cd): Candela is the SI unit of luminous intensity and is defined by the fixed value of the luminous efficacy.
It should be noted that these 7 units are assumed to be mutually independent and hence are called base units.
Drive Units :
The unit which are derive by base units.
For example
|
S NO |
Name Drive Quantity |
Name of SI Units |
SI Units Symbol |
|
1 |
Force |
Newton (N) |
kg.m/s2 |
|
2 |
Acceleration |
Meter per second Square |
m/s2 |
|
3 |
Velocity |
Meter per second |
m/s |
|
4 |
Momentum |
Kilogram Meter per second |
kg.m/s |
|
5 |
Power |
Kilogram Meter per second Square |
kg.m2/s |
|
6 |
Work |
Newton per second |
N/s |
|
7 |
Pressure |
Newton per meter square |
N/m2 |
These were a few widely used units along with their SI units. Apart from these units, there are certain additional units that are commonly seen in physics.
MCQz
1. Which of the following is derive physical quantity?
(a) lenght (b) mass (c) time (d) speed
2. Which of the following is base physical quantity?
(a) Acceleration (b) Velocity (c) Time (d) Speed
3. The physical quantity on the basis of which other quantity are form are called __________________?
(a) base quantity (b) drive quantity (c) acceleration (d) time
4. The SI unit of acceleration?
(a) m2 (b) m/s2 (c) m/s (d) m.s
Questions
- What are Physical Quantities?
- What are base physical quantities?
- What are derive quantities?
- What is System International (SI)?
- What are base units?
- What are derive units?
Answer These questions in comment box.
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