# Derived Units: Similarities and Differences with Fundamental Units

#### Academic Questions in PhysicsPlease check out our Test Your Knowledge page to see all Questions and Answers The Law of Inertia is also referred to as _____. A. 1st Law of Thermodynamics B. 2nd Law of Thermodynamics C. 3rd Law of Thermodynamics D. Newton's 1st Law of Motion E. Newton's 2nd Law of Motion F. Newton's 3rd Law of Motion The process whereby the velocity of an object increases and decreases over a period of time is best associated with the term _____. A. Speed B. Velocity C. Momentum D. Constant Velocity E. Acceleration F. Average Velocity The rate of motion is best referred to as _____. A. Speed B. Velocity C. Momentum D. Inertia E. Acceleration F. Constant Velocity Consider this expression below: A body X exerts a force FX on another body Y. In return, body Y exert a force FY back on body X. The forces FX and FY are equal in magnitude but opposite in direction. Putting the above expression into equation: FX = -FY Where FX is the action force FY is the reaction Force The above expression relates to _____. A. Theory of Force B. Force Postulate C. Einstein's proposal on Relativity D. Newton's 1st law of motion E. Newton's 2nd law of motion F. Newton's 3rd law of motion The tendency of a body to remain in a state of rest or in uniform motion is referred to as _____. A. tension B. uniform acceleration C. constant acceleration D. deceleration E. inertia F. velocity A change in the position of an object with reference to time is best described as _____. A. momentum B. displacement C. velocity D. acceleration E. direction F. motion The saying "what goes up on earth must come down" can be best attributed to _____. A. force B. motion C. mass D. acceleration E. average velocity F. constant velocity We have _____ laws of Thermodynamics. A. 1 B. 2 C. 3 D. 4 E. 5 D. 6

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### What are Derived Units?

Derived units are the units of derived quantities. They are dependent on fundamental quantities and are expressed from the combination of two or more fundamental units.

As the name implies, derived units are always derived (from fundamental units). For instance, velocity is a quantity whose unit is derived from length and time (both of which are fundamental quantities) as summarized in the paragraph below.

• Length (which could also mean distance) is a fundamental quantity measured in meters (m) while time is another fundamental quantity measured in seconds (s). To this end, the unit of velocity is meter per second (m/s) because it's derived from the fundamental units (length and time) respectively.

Note: Since derived units are always derived from fundamental units, we cannot have "feet per second" as the unit of velocity. This is because the unit feet isn't the ideal measurement for length (or distance); although it may be used as a unit of measurement in some cases.

Examples of some derived quantities and their units:

The diagram below shows some derived quantities, their respective derived unit and the symbol of such unit. For instance, the first derived quantity from the table is area. The derived unit for area is meter square (or square meter) whose symbol is m2. Note: It's important to state that the unit of area (m2) is derived from the length which happens to be a fundamental unit.

### Similarities between Fundamental and Derived Units

1. Both units are used to express physical quantities.

2. Both are recognized as the Standard International System of Units (SI Units).

### Differences between Fundamental and Derived Units

1. Fundamental units are independent of every other unit including themselves while derived units are dependent on fundamental units.

2. Fundamental units cannot be further broken down while derived units can be broken down.

3. We have only 7 fundamental units while derived units are much more in number.

4. Fundamental units are uniquely expressed while derived units are expressed in terms of fundamental units. Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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