Chapter 1
Physics, the
Fundamental Science
Lecture PowerPoint
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Objectives of Physics
 To find the limited number of fundamental
laws that govern natural phenomena
 To use these laws to develop theories that
can predict the results of future
experiments
 Express the laws in the language of
mathematics

Mathematics provides a bridge between
theory and experiment
 Physics predicts how nature will behave in one situation
based on the results of experimental data obtained in
another situation.
 Physics experiments involve the measurement
of a variety of quantities.
 These measurements should be accurate and
reproducible.
 Physics is exact science
 The first step in ensuring accuracy and reproducibility
is defining the units in which the measurements are
made.
Subfields of Physics
 Classical Physics
 Mechanics - forces and motion
 Thermodynamics - temperature, heat, energy
 Electricity and Magnetism
 Optics - light
 Modern Physics
 Atomic physics - atoms
 Nuclear physics - nucleus of the atom
 Particle physics - subatomic particles: quarks, etc
 Condensed matter physics - solids and liquids
Units
 To communicate the result of a
measurement for a quantity, a unit must
be defined
 Defining units allows everyone to relate
to the same fundamental amount
System of Measurement
 Standardized systems
 agreed upon by some authority, usually a
governmental body
 SI -- Systéme International
 agreed to in 1960 by an international committee
 main system used in this text
 also called mks for the first letters in the units of
the fundamental quantities
 Length
 Units: SI – meter, m
 Mass
 Units: SI – kilogram, kg
 Time
 Units: SI – seconds, s
 Electric Current
 Units: SI – Ampere, A
There are three base units more, but we
are not going to use them (mole, kelvin
and candela)
Fundamental Quantities
and Their Units
Quantity
SI Unit/abbreviation
Length
Meter (m)
Mass
Kilogram (kg)
Time
Second (s)
Electric Current
Ampere (A)
Absolute Temperature
Kelvin (K)
Luminous Intensity
Candela (Ca)
Amount of Substance
Mole (M)
Prefixes
 Prefixes correspond to powers of 10
 Each prefix has a specific name
 Each prefix has a specific abbreviation
 The General Conference on Weights
and Measurements recommended the
prefixes shown
 Examples:
Write the following lengths in meters :
a)
b)
c)
d)
e)
62.8 km = 62.8*103 In Scientific Notations 6.28*104
33.3 nm = 33.3*10-9 m;In Scientific Notations 3.33*10-8
13.6mm =13.6*10-6 m In Scientific Notations 1.36*10-5
2.5 mm = 2.5*10-3 m
3.1 *103 cm = 3.1*103*10-2 = 31 m
 Write each of the following numbers
using the appropriate prefix:
 a) 1.2*106 Hz = 1.2MHz
 b) 3.2 *10-9 s = 3.2 ns
 c) 4.5 *103 m = 4.5 km
 d) 6.8 *10-3 m = 6.8 mm
Dimensional Analysis
 Technique to check the correctness of
an equation dimensionally
 Cannot give numerical factors: this is its
limitation
 Dimensions (length, mass, time,
combinations) can be treated as
algebraic quantities

add, subtract, multiply, divide
 Both sides of equation must have the
same dimensions
 Example
x= vt2 x is the distance in meters, v is the speed in
m/s and is the time in seconds. Is this equation
correct dimensionally?
Distance is in meters thus the right hand side of the
equation MUST be in meters.
x= vt2
m m/s*s2= m/s ; the left hand side is in meters the
right hand side is m/s thus this equation is NOT
correct.
Example:
x= 1/2at2 Is this equation correct dimensionally?
 m =m/s2*s2 =m thus this equation is correct
a= acceleration iti sin m/s2
Conversions
 When units are not consistent, you may
need to convert to appropriate ones
 Units can be treated like algebraic
quantities that can “cancel” each other
 See the inside of the front cover for an
extensive list of conversion factors
 Example: A car travels through a school zone
at a speed of 25mil/h. What is this speed in
km /h, and in m/s?
 Conversion factors: 1 mil=1.6 km,
1km=1000m
 25mil*1.6km/mil.h = 40 km/h
 40km/h *1000m/km *1/(60*60)s/h=11.11 m/s
Pythagorean Theorem
 The sides of a right angle triangle are
related according to Pythagorean
Theorem as follows;

r2 = x 2 + y 2
r
y
x
Problem Solving
Strategy
 Rules for rounding off numbers
 Consider the first number to the right of
the required number if
 This number is less than 5, then the
preceding digit remains the same
 Example: 2.674998765  2.67
 If this number equal to or greater than 5
then add one to the preceding digit.
 2.350012.4