Physics

Fundamental Quantities and Units in Physics

len Alfred Ajibola - 07th February, 2019 @ 06:22 PM

Topics in Physics

Derived Units: Similarities and Differences with Fundamental Units Gravity: Interesting facts on Gravity Relative Density of Substances and Specific Gravity Types of Heat Transfer: Conduction Types of Heat Transfer: Convection Types of Heat Transfer: Radiation Physics Scheme of Work, SS1, First Term Physics Scheme of Work, SS1, Second Term Physics Scheme of Work, SS1, Third Term Velocity and Acceleration Newton's Laws of Motion Importance of Gravity What is Density? Density of various Substances Concepts of Force and Motion Motion and Speed Concept of Heat Transfer Concepts of Heat and Temperature Gravity: What is Gravity? Zeroth Law of Thermodynamics - Thermal Equilibrium Fundamental Quantities and Units in Physics


Academic Questions in Physics

Please check out our Test Your Knowledge page to see all Questions and Answers

The rate of change of momentum is proportional to the applied force and will take place in the direction of that force.

The above statement is attributed to _____.

  • A. Albert Einstein

  • B. Isaac Newton

  • C. Galileo Galilei

  • D. Neils Bohr

  • E. Ernest Rutherford

  • F. Marie Curie

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

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What are Units in Physics?

Anything that can be measured must have a unit of measurement. For instance, it isn’t right to say “I weigh 65”. Based on this fact, units are means of measurement. Anything measurable is termed a physical quantity.

Please read on Important concepts in Physics here.

The analogy below explains a physical quantity and its unit:

  • Let’s imagine you wish to buy uncooked rice in a local store around you. (Rice is the physical quantity to be measured here). Before you buy the specific quantity of rice; it's first measured (let’s say "one cup" for instance) before it's sold to you. In this case, "one cup" is the unit of measurement (quantity of rice to be bought).

  • Using the sport of boxing as another instance; we have different categories like feather weight, light weight and heavy weight. All of these categories are made possible because the mass (weights) of the individuals involved have been measured via a unit.
    Please read on the Concept of Mass and Weight here.

Fundamental and Derived Units are internationally recognized as units of measurement. This is why they are also called the Standard International Unit (SI Unit).


Please read on Derived Units, its Similarities and Differences with Fundamental Units here.

Note: In physics, understanding fundamental and derived units are very important because the properties of physics are represented only by their units in equations.

You can read on Molecular Mass explained with worked examples here.


What are Fundamental Units?

Fundamental units are the units of fundamental quantities.

A fundamental unit is a unit that does not depend on any other unit; neither can it be changed nor is related to another fundamental unit.

Note: A fundamental unit is also referred to as a basic unit.

Fundamental Units are always constant. This means that they don't change, (remains the same) and are standardized all over the world. The fundamental quantities alongside their respective fundamental unit are 7 in number. They include:

  1. Mass (m) is a fundamental quantity whose unit is kilogram (kg)
  2. Length (l) is a fundamental quantity whose unit is meter, (m)
  3. Time (t) is a fundamental quantity whose unit is second (s)
  4. Temperature (T) is a fundamental quantity whose unit is Kelvin (k)
    You can read on the Concept of Temperature and Heat here.

  5. Electric Current (I) is a fundamental quantity whose unit is ampere (A)
  6. Amount of Substance (n) is a fundamental quantity whose unit is mole (mol)
  7. Luminous Intensity (|v) is a fundamental quantity whose unit is candela (cd)

The table below shows the fundamental quantities (with their symbols) and the respective fundamental units (with their symbols):
Fundamental Units - Len Academy

The above (7 fundamental units) cannot be broken down into elementary or smaller unit. In short, they are the most basic units of measurement.

Note: Although the fundamental and derived units are internationally recognized, some countries may still choose to use a different unit for measuring the same quantity. Regardless the unit that has been chosen, it must however, still be convertible to its respective fundamental or derived unit via a constant factor. For instance:

  • The units yard and feet may be used to measure length; but meter still remains the fundamental unit of length.
  • Similarly, while pounds may be used to measure mass; kilogram still remains its fundamental unit thus making it globally recognized and accepted as the basic, standard and fundamental unit for measuring mass.

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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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Amazing facts in Physics

Glass Ball - Len Academy

Glass Balls actually bounce higher than Rubber Balls

Every planet has its own unique gravitational force. For instance, Mars has a gravity of 3.711 m/s2 while earth’s gravitational force is 9.807m/s2.

Please read on gravity here

When two metals are put together in space, they will stick together as if they are welded. This phenomenon is called cold welding

The fastest animal on land is Cheetah. It can reach a maximum speed of about 113km per hour.

Please read on motion, speed, velocity and acceeration here


NOTABLE POINTS IN Physics

The Classical Mechanics (Laws of Motion) is a fundamental part of Physics.

Below are the Newton's Laws of Motion:

An object at rest will continue in its state of rest; while an object in uniform motion will continue in a straight line, unless an external force acts on it.

Newton's First Law of Motion.

Please read on Motion and Speed here.

The rate of change of momemtum is proportional to the applied force and will take place in the direction of that force.

Newton's Second Law of Motion.

To every action, there is an equal and opposite reaction.

Newton's Third Law of Motion.

Please read on Newton's Laws of Motion here.

The study of Thermodynamics revolves around the relationship between heat, temperature, energy and mechanical work; and these can be summarised under the 4 laws of Thermodynamics (Numbered zero through three).

You can read on the Concepts of Heat and Temperature here.

Below are the 4 laws of thermodynamics:

Zeroth law of thermodynamics – If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

Please read on the Zeroth Law of Thermodynamics here.

1st law of thermodynamics – Energy can neither be created nor destroyed but can be changed from one form to another.

You can read on the Food Chain here.

2nd law of thermodynamics – The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

3rd law of thermodynamics – As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Fuses are present in many electrical devices. They are basically 🔥 fire-breakers 🔥

If there is a power surge, the fuse will break, preventing damage to the electrical devices. It will also prevent the incidence of 🔥 fire🔥 on or from such device.

Physics is one of the core sciences.

Physics is defined the scientific study of matter and the movement of matter through the space and time of the universe.

Understanding the basic and fundamental concepts of physics will help you better comprehend this subject. Below are some of the concepts:

  1. The Laws of Motion (Classical Mechanics)
  2. Electromagnetism
  3. Relativity
  4. Thermodynamics

Please read on the basic introduction of the above physics concept here