LESSON 1 ( Physics 101 )

Physics is a major science, dealing with the systematic study of the basic properties of the universe, the forces they exert on one another, and the results produced by these forces. It is the remaining core of naturl philosophy and concerns itself with questions of what underlies the interactions of matter, energy, space and time, and even with what constitutes reality. It is not surprising that a field that has produced the theories of relativity and quantum mechanics and has drastically altered our concept of the universe has an aura of mystery --- of being remote from everyday experience and impossible to understand. Once one becomes accustomed to looking for an explanation of various phenomena in terms of underlying scientific principles, it is possible to see physics everywhere. The flight of birds, the operation of a microwave oven, the color of the sunset, and the pitch of one’s voice all have basic explanations in physics. Those explanations can be understood by anyone, not just professional scientists.

           Physics is closely related to the other natural sciences and, in a sense, encompasses them. Chemistry, for example deals with the interaction of atoms to form molecules. Much of modern geology is largely a study of the physics of the earth and is known as geophysics. Astronomy deals with the physics of the stars and outer space. Even living systems are made up of fundamental particles and, as studied in biophysics and biochemistry, they follow the same type of laws as the simpler particles traditionally studied by a physicist.

The emphasis on the interaction between particles in modern physics, known as the microscopic approach, must often be supplemented by a macroscopic approach that deals with larger elements or systems of particles. This macroscopic approach is indispensable to the application of physics to much of modern technology. Thermodynamics, a branch of physics developed in the 19^th century, deals with the elucidation and measurement of properties of a system as a whole and remains useful in other fields of physics; it also forms the basis of much of chemical and mechanical engineering. Such properties as the temperature, pressure and volume of a gas have no meaning for an individual atom or molecule; these thermodynamic concepts can only be applied directly to a very large system of such particles. A bridge exists, however, between the microscopic and macroscopic approach; another branch of physics; known as statistical mechanics, indicates how pressure and temperature can be related to the motion of atoms and molecules on a statistical basis.  

Physics emerged as a separate science only in the early 19^th century, until that time a physicist was often also a mathematician, philosopher, chemist, biologist, engineer, or even primarily a political leader or an artist. Today, the field has grown to such an extent that with few exceptions modern physicists have to limit their attention to one or two branches of the science. Once the fundamental aspects of a new field are discovered and understood, they become the domain of engineers and other applied scientist. The 19^th century discoveries in electricity and magnetism, for example, are now the concentrations of electrical and communication engineers; the properties of matter discovered at the beginning of the 20^th century have been applied in electronics; and the discoveries of nuclear physics, have passed into the hands of nuclear engineers for applications to peaceful or military uses.

MATHEMATICS as a language of science

     Mathematics is the language of physics; that is when ideas in science are expressed in mathematical terms:        

                   1. They are unambiguous.    

                   2. They do not have double meanings, that so often confuse the discussion of ideas expressed in

                        common language.

                   3. They are easier to verify or disprove by experiment.

                   4. The methods of mathematics and experimentation led to enormous success in science.

                   5. The abstract mathematics developed by mathematicians is often years later found to be the

                         exact language by which nature can be described.

    Mathematics is the language of physics does not mean that mathematics is physics or physics is mathematics.

THE SCIENTIFIC METHOD – is a method that is extremely effective in gaining, organizing, and applying new knowledge. The steps are :

1.      Recognize a problem.

2.      Make an educated guess --- a hypothesis. Hypothesis is an educate guess that is only considered factual after it has been demonstrated by experiments. If a hypothesis has been tested over and over again and has not been contradicted it may become known as a law or principle.  

3.      Predict the consequences of the hypothesis

4.      Perform experiments to test predictions.

5.      Formulate the simplest general rule that organizes the three main ingredients --- hypothesis, prediction, and experimental outcome --- into a theory.

The success of science has more to do with an attitude common to scientists than with a particular method. This attitude is one of inquiry, observation, experimentation and humility.

THE DOMAIN OF PHYSICS

A.  According to size of objects studied

     1.  Quantum domain – the domain of small objects. Objects are considered small if their sizes are

            comparable to or smaller than the size of an atom.

     2.    Non-quantum domain – the domain of large objects. Objects are considered large if they are larger 
             than the size of an atom.

B.  According to speed of objects studied

     1.  Relativistic domain – the domain at high speed, that is if the speed of the moving object is 
          comparable to the speed of light.

     2. Non-relativistic domain – the domain at low speed, that is the speed of the moving object is less than 
          the speed of light.

            

C.  Newtonian domain – a combination of the division according to size and speed. It is the domain of large

            objects at low speeds, the one we deal in our daily lives. (In honor of Sir Isaac Newton, the 17^th century physicist who played the key role in developing the physics of large objects moving at low speed).

            

D.  Mechanics – is the study of the relation between the force and the resulting motion. It seeks to account  

               quantitatively for the motion of objects having given properties in terms of the force acting on them.

      1.  Newtonian mechanics – is the mechanics of the Newtonian domain. It deals with systems containing 

            objects which are large and which move at low speed.

2. Relativistic mechanics – is the mechanics of the relativistic domain. In 1905, Einstein showed that a     different approach was necessary for the study of objects moving at speeds so high as to be                  comparable to the speed of light.

      3. Quantum mechanics – is the mechanics of the quantum domain. It was developed about the same time

           with relativistic mechanics by Max Planck, Louis de Broglie, Erwin Schrodinger and others. They 
           found out that the Newtonian mechanics could not explain the motion of objects whose size is in the 
           atomic scale or smaller.

 E.   Electromagnetism – is the study of the properties and consequences of the electromagnetic force, 
         which is one of the fundamental forces in nature. The fundamental forces are gravitational force, 
         electromagnetic force, strong nuclear force and weak nuclear force.

 F.   Solid-state physics is a branch of physics that deals with the properties of solids. A particular problem 

            in solid – state physics, for instance the properties of materials use in transistors, is solve by 

            employing the mechanics of whichever domain is most appropriate.  

 G.  Heat  and Thermodynamics

   THE FUNDAMENTAL MEASURABLE QUANTITIES IN PHYSICS

    1.  Length           3.  Time                   5.  Luminous intensity             7.  Molecular quantity

    2.  Mass             4.  Temperature        6.  Electric charge ( current )

   THE FUNDAMENTAL MEASURABLE QUNATITIES IN MECHANICS

               1.  Length                 2.  Mass                       3.  Time

  Measurement is a scientific comparison between an unknown quantity to a fixed known quantity called standard.

 Systems of Measurement

1.      English system  (British Engineering system) – originated in England

2.      Metric system – originated in France

  Systeme International d’Unites ( SI ) adopted by  the International Bureau of Weights and Measures in 
  1960.  The units of the MKS is adopted as the base units of the SI system.

Base Units of each System of measurement

Measurable Quantities in Mechanics	Metric System		English System
	CGS	MKS	FPS
Length	Centimeter ( cm )	Meter ( m )	Foot ( ft )
Mass	Gram ( g )	Kilogram (kg )	Slug ( lbm )
Time	Second ( s )	Second ( s )	Second ( s )

Reasons for adopting the Metric system:

1.      It is scientifically planned.

2.      It is a decimal system.

3.      It is universally accepted.

 DISADVANTAGES OF THE ENGLISH SYSTEM

            1 yard = ( King Henry I ) distance from the tip of his nose to the end of his thumb

            1 inch ( 1324 ) = length of three grains of barleycorns laid end to end

            1 mile = 1000 double step of an average soldier

            1 foot = length of the foot of the king

THE CONCEPT OF THE METER

                       To be discuss in class with demonstrations

MAKING AND RECORDING MEASUREMENTS

Reasons for uncertainty in Measurements

1.      The limitations inherent in the measuring instrument.

2.      The conditions under which the measurement was made.

3.      The different ways under which the person uses or reads the measuring instrument.

Terminologies:

1. Fundamental or base unit – the standard unit for length, mass and time.
2. Derived unit a combination of any of the three fundamental base units; i. e.  m/s, m/s²,  ft², m³ etc.
3. Accuracy – refers to the closeness of a measurement to the standard value for a specific physical quantity. It is express either as an absolute error or relative error.
4. Absolute error ( E_A ) is the actual difference between the observed ( O ) or measured value and the accepted value ( A ).

                                                      E_A = | O – A |

5. Relative error ( E_R ) I expressed as a percentage error and is often called a percentage error.

                                                      E_R = E_A/A

6. Absolute deviation ( DA ) is the difference between a single measured value ( O ) and the average ( M ) of several measurements made in the same way.

                                                                                                           

                                                      D_A = | O – M |

7. Relative deviation ( D_R ) is the percentage average deviation of a set of measurements.

                                                      D_R = D_A / M

8. Precision is the agreement among several measurements that have made in the same way. It tells how much reproducible the measurements are and is express in terms of the deviation.
9. Tolerance is the degree of precision obtainable in a measuring instrument.
10. Significant figure are those digits in a number that are known with certainty plus the digit that is uncertain.