Physics begins with observations of the natural world and experiments to gather facts. Physicists develop concepts, laws, and theories to explain these facts. Concepts are measurable quantities like length, energy, and atoms. Laws summarize relationships between concepts, such as Hooke's law relating force and spring compression. Theories are explanatory models used when direct observation is not possible, like wave theory of light. Physics aims to understand nature through developing and testing such conceptual frameworks.

1. Ref: Tom Duncan Advanced
PHYSICS
About physics 1
Like other sciences Physics starts with
observations in the world around us or from
laboratory experiments (often involving
measurements) designed to obtain facts.

2. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
Structure of physics – Week 1
• Like other sciences Physics starts with
observations in the world around us or from
laboratory experiments (often involving
measurements) designed to obtain facts.
• For example the investigation of electricity -
began when it was noticed that amber (a glass-
like fossil) attracts small light objects when it is
rubbed with cloth.

3. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
Observations in the world around us
• Optical microscope Electron microscope

4. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
• Concepts helps to explain facts of physics and explain the behaviour of
the physical world. Physicists invent these terms called concepts. These
concern quantities that can be measured. Some concepts like length are basic
while others , like potential difference (p.d.) in electricity are less ‘concrete’
and require more sophisticated measuring instrument.
• Four of the most useful concepts are:-
• Atoms
• energy
• Fields
• waves
• They pervade the whole of physics, enables us to build an intellectual
framework that help us to understand a wide range of phenomena.

5. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
• Laws or principles:- exists between concepts
• They summarize a large number of facts in an economical way, often
as a mathematical equation.
• Hooks’s law:- relates the concepts of force and length and tells us
how a spring behaves when it is stretched.
• Boyle’s law:- describes how gases respond when squeezed, using the
concepts of pressure and volume.
• Newton’s laws of motion:- deals with the action of forces and objects
often called (‘bodies’) and the acceleration they may produce.
• Ohm’s law in electricity:- connects the concepts of potential
difference and current
Isaac Newton (1643-1727)Robert Hooke (1635-
1703)

6. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
These so-called ‘laws of nature’ are formulated by scientists
by extracting from the facts and they do have limitations.
Thus, Hook’s law is true only if the spring is not stretched
too far.
Newton’s laws of motion do not hold for bodies moving at
speeds near that of light and
Ohm’s law only applies to certain conductors.
However introducing concepts and discovering laws, we are
able to make the physical world seem reasonable and to
obtain some control over it.

7. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
Theories:-
When we are dealing with things not directly accessible to our senses we
sometimes use theories or ‘thought models’ to help us to explain
things.
e.g. Wave theory is used to make sense of some of the properties of light
and sound, and draws on our knowledge of the behaviour of ‘real’
waves such as surface water waves.
The field theory enables us to deal with the invisible, action-at-a-distance
(non-contact) forces occurring in electricity, magnetism and
gravitation.
The kinetic theory gives us insight into the properties of matter in bulk,
that it helps to relate macroscopic (large-scale) properties such as
density and pressure, to the masses, speed, energies, etc. of the
constituents atoms and molecules that cannot be seen directly.

8. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
Theories:-
Note: scientific theories are like geographical maps
that aids to understand and are representation or
analogies of reality and are not complete
descriptions of it.
They can be used as a means of abstraction of the
real world objects – as in OOP.

9. 10/10/13 by Dr. RDP 2008 ref. T. Duncan
About physics
Branches of Physics:-
For study we often divide physics into different
branches such as mechanics, heat, light, sound,
electricity, etc.
Many concepts and laws are useful in more than one
branch.

10. 10/10/13 by RDP 2013 ref. T. Duncan
About physics
Questions to do:-
(i) Explain the following terms in physics, giving example
of each terms
(a) Concepts
(b) Laws
(c) Theories