1.Definition
2.Characteristics 3.Branches
4.Models, Theories, laws 5.Measurement
At the end of this chapter, you should be able to
1) Define PHYSICS;
2) Explain MEASUREMENT;
3) Implement Unit Conversions in problem solving.
We know that they can be explained by Physics
BUT WHAT
IS
MATTER
TIME
SPACE ENERGY
Definitions of PHYSICS
Is the science of matter and energy and
their interactions
Is governed by laws and formalisms that
explains the phenomena of the exotic
and of the everyday life
SCIENCE
from Latin word “scientia” meaning “knowledge” a systematized knowledge derived from
observation, study, facts, and principles.
PHYSICS
meaning “natural things”
Physics, major science, dealing with the
fundamental constituents of the universe,
the forces they exert on one another, and
the results produced by these forces.
“ The object of all sciences is to coordinate our experiences and to bring them into a logical system.”
Every Science…. Scientific Method:
Chooses to study a class of phenomena
Describe in a systematic way
‘explain’ in terms of principles
Collection of Data
Formulation of Laws
Formulation of a Model, Theory or Conceptual
MODELS - mental image of a
phenomena in terms of something we are familiar with.
THEORIES - attempt to solve a set of problems, often with mathematical precision.
Search for the truth
Creative human activity Investigative
Empirical Numerical
Physics, the most fundamental science, is
concerned with the basic principles of the Universe.
It is the foundation upon which the other
Mechanics
deals with such ideas as inertia, motion, forces and energy.
Thermodynamics
deals with the principles on heat flow, heat transformations and temperature measurements.
Electricity and Magnetism
deals with other aspects of matter and space with emphasis on electric charge and current.
Optics
concerned with the nature and propagation of light The ability not only to define, but to measure is a requisite of science
In Physics, more than in any other field of knowledge,
the precise definition of terms and accurate
PHYSICAL QUANTITY
any number that is used to describe a physical phenomenon quantitatively.
Fundamental Quantities
– quantities that exist
by themselves.
Time, Length, Mass
Derived Quantities
– quantities that are
dependent on other quantities.
FUNDAMENTAL QUANTITIES DISTANCE TIME
MASS
TEMPERATURE
AMOUNT OF MATTER
CURRENT
Scalar Quantities- quantities with magnitude only Vector Quantities- quantities with both magnitude
►
Standards
-
we can refer to standards as
the
reference
from which
you will compare your
physical quantity of interest
Standards
UNITS
The problem here is that
SI (Système Internationale)
is the system universally used by the scientific
community
SI
English
Time :
Standard : 1 second
Definition : the time required for the
9 192 631 770 cycles of Cs – 133 atom
Length
Standard : 1 meter
Definition : the distance traveled by light in vacuum in
during a time interval of 1/299 792 458 of a second
Mass
Standard : 1 kilogram
Definition : The mass of the International kilogram
prototype kept at the France’s International Bureau
Measurement
instruments, when
calibrated in terms of the standard, give a very good
approximation of the standard!
Remember to choose measurement instruments wisely - not all instruments that can measure length, can
It is better to use prefixes in
WHAT IF... You are driving
along a highway and you
see a sign that says
“SPEED
LIMIT 100 mi/h”
and your
speedometer indicates that
your speed is about 31
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 out
There are three types of conversion
1. Straight forward Linear Conversion 36 in = ____ cm
2. Chain Conversion 12 mi/h = ____ m/s
3. Power Conversion 21 in2 = ____ cm2
The speed of a 2.0 kg ball is 450 km/h. Determine its speed in
a. m/s
b. ft/s
Identify the starting point Identify the “destination”
List the connecting conversion factors
Multiply the starting measurement by the
conversion factors
Dimension
denotes the
physical nature
of
a quantity
Dimensions
can be treated as algebraic
quantities
Always remember that
equations should
Quantity Dimension
Unit
Length
L
Meter (m)
Mass
M
Kilogram (kg)
Dimensional analysis
makes use of the fact that dimensions can be treated as
algebraic quantities.
Is a process of
algebraic
manipulation of
Determine the dimension of the quantity a. v = at
b. x = xo + vot + (½) a t2
c. D = m/V
where
[a] = L/T2
Make an equation with the following specifications:
1. At the left hand side is W and X (Work, same dimensions as energy [ML2/T2], X is distance)
2. At the right hand side is mass (m) and acceleration (a)
