Definition of Physics

• Physics, the most fundamental science, is concerned with the basic principles of the Universe. It is one of the foundations on which the other physical sciences – astronomy, chemistry, and geology – are based.

• Physics is the study of the properties and nature of matter, the different forms of energy and the ways in which matter and energy interact in the world around us. To understand physics, we need to know Model, Theories and Laws in describing a phenomenon.

• The study of the laws that determines the structure of the universe with reference to the matter and energy of which it consists. It is not concerned not with chemical changes that occur but with the forces that exist between objects and the interrelationship between matter and energy.

The goal of Physics

The goal of Physics is to provide an understanding of nature by developing theories based on experiments

The beauty of Physics• The beauty of Physics lies in the simplicity of its fundamental theories

and in the way just a small number of basics concepts, equations, and assumptions can alter and expand our view of the world

The areas of PhysicsPhysics can be divided into five areas: • Mechanics :- which is concerned with the effects of forces on material objects. Also covers the main

concepts of physics, e.g. forces, energy and the properties of matter.• Thermodynamics :- which deals with heat, temperature, and the behavior of large numbers of particles.

Also explains heat energy in terms of its measurement and the effects of its presence and transference. Includes the gas laws.

• Electromagnetism :- which deals with charges, currents, and electromagnetic fields. Also explains the forms, uses and characteristics of these two linked phenomena.

• Relativity (Year : 1905) :- a theory that describes particles moving at any speed, and connects space and time

• Quantum Mechanics (Year: 1900) :- a theory dealing with behavior of particles at the submicrospic level as well as the macroscopic world

• Since the turn of the century, however, quantum mechanics and relativistic physics have become increasingly important; the growth of modern physics has been accompanied by the studies of atomic physics, nuclear physics (1896) and particle physics.

Some terms of Physics

• Astrophysics : - The Physics of astronomical bodies and their interactions. Astrophysics also studies the physical and chemical processes involving astronomical phenomena. Astrophysics deals with stellar structure and evolution (including the generation and transport of energy within stars), the properties of the interstellar medium and its interactions with stellar systems, and the structure and dynamics of systems of stars and systems of galaxies.

• Geophysics : - The branch of science in which the principles of mathematics and physics are applied to the study the earth’s crust and interior. It includes the study of earthquake waves, geomagnetism, gravitational fields, and electrical conductivity using precise quantitative principles. In applied geophysics the techniques are applied to the discovery and location of economic minerals (e.g. petroleum).

• Biophysics :- The study of the physical aspects of biology.• Theoretical Physics : - The study of physics by formulating and

analyzing theories that describe natural processes. Theoretical physics is complementary to the study of physics by experiment.• Experimental Physics : - The study of physics by experiment• Mathematical Physics :- The branch of theoretical physics concerned

with the mathematical aspects of theories in physics• Thinking Physics : - The study of Physics which emphasis more on

critical thinking and teaching physical concepts

• Laws :- A law is a descriptive principle of nature that holds in all circumstances covered by the wording of the law. Some laws are named after their discoverers (e.g. * Boyle’s law); some laws, however, are known by their subject matter to describe them (e.g. * the law of conservation of mass), while other laws use both the name of the discoverer and the subject matter to describe them (e.g. * Newton’s law of gravitation).• Theory :- A description of nature that encompasses more than one law but has not

achieved the uncontrovertibly status of a law . Theories are often both eponymous and descriptive of the subject matter (e.g. Einstein’s theory of relativity and Darwin’s theory of evolution).• Hypothesis :- A theory or law that retains the suggestion that it may not be

universally true. Some hypothesis about which no doubt still linger have remained hypotheses ( e.g. Avogadro’s hypothesis ) for no clear reason.

Dimensions : complete the tableDerived quantity Equation /relation/

formulaDerived Unit SI Unit Dimension

Velocity Displacement / time ms-1 ms-1 LT-1

Acceleration

Force Mass x acceleration Kg ms-2 Newton

Pressure

Energy / work

Strain

Power

Electrical potential differenceElectic resisitance

The uses of Dimension …• Checking the homogeneity of an equation• Dimensional analysis Derivation of physical equation

Check… dimensionally consistent / homogeneous• v = u + 2as• v2 = u + 2as• v = 2as• v2 = u2 + 2as