WHAT IS GENERAL
PHYSICS?
At the end of the lesson, you will
be able to:
•
•
•
•
Introduction & Definition of Physics;
Convert units from SI to English & vice versa;
Recall rounding-off of numbers;
Designate multiples and subdivisions of any
using prefixes;
• Identify significant figures;
• Express numbers in scientific notation.
General Physics
• Physics investigates concepts of energy
involved in everyday life.
General Physics
• General Physics is designed for students
interested in science and technology related
careers and majors.
General Physics
• It is taught at the algebra/trigonometry level
and it incorporates conceptual understanding,
laboratory work, and mathematical problem
solving.
General Physics
• General Physics I covers motion, heat, and
wave motion.
Physics
•
•
Its goal is to describe all phenomena in the physical world in terms of a
few fundamental relationships (laws of physics) between measurable
properties of matter and energy.
Physicists use numbers to describe measurements. Such a number is
called a physical quantity. However, a physical quantity would make sense
to everyone when compared to a reference standard.
All phenomena in the
physical world
Quantitative results
Physical Laws
Mathematical form
Theories and Experiments
• The goal of physics is to develop theories based on
experiments
• A physical theory, usually expressed mathematically,
describes how a given system works
• The theory makes predictions about how a system
should work
• Experiments check the theories’ predictions
• Every theory is a work in progress
What are Physical Quantities?
Physical Quantity
• Are those quantities can be measured, this are
quantities that are use to describe the laws of
physics.
Physical Quantity
Symbol for
Quantity
Unit
Symbol of Unit
Length
l
Meter
m
Mass
m
Kilogram
kg
Time
t
Second
s
Electric Current
I
Ampere
A
Temperature
T
Kelvin
K
Luminous Intensity
Iu
Candela
cd
Amount of Substance
n
Mole
mol
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.
SI System of Measurement
• SI – Systéme International
– Since 1960, the system of units
used by scientists and engineers
is the “metric system”, which is
officially known as the
“International System” or SI
units (French term).
Fundamental Quantities and Their
Dimension
• Mechanics uses three fundamental quantities
– Length [l]
– Mass [m]
– Time [t]
Length
• Units
– meter, m
• The meter is currently defined in terms of the
distance traveled by light in a vacuum during a
given time.
– 1 m is defined as the distance travelled by light in
a vacuum in 1/299,792,458 second. Based on the
definition that the speed of light is exactly
299,792,458 m/s.
Time
• Units
– seconds, s
• The second is currently defined in terms of the
oscillation of radiation from a cesium atom.
– 1 second is defined as 9,192,631,770 cycles of the
microwave radiation due to the transition
between the two lowest energy states of the
Cesium atom.
Mass
• Units
– kilogram, kg
• The kilogram is currently defined as the mass
of a specific cylinder kept at the International
Bureau of Weights and Measures.
– 1 kg is defined to be the mass of a cylinder of
platinum-iridium alloy at the
International Bureau of
Weights and Measures.
Other Systems of Measurements
• cgs – Gaussian system
– Named for the first letters of
the units it uses for
fundamental quantities
• US Customary
– Everyday units
– Often uses weight, in pounds,
instead of mass as a fundamental
quantity
Convert the following expressions:
1. 28 oz to g
Convert the following expressions:
2. 3 ft to cm
Convert the following expressions:
3. 10 km to mi
Convert the following expressions:
4. 2 kg to oz
Prefixes
• Prefixes correspond to powers of 10
• Each prefix has a specific name
• Each prefix has a specific abbreviation
Prefixes
• In certain cases, particularly
in scientific usage, it
becomes convenient to
provide for multiples larger
than 1000 and for
subdivisions smaller than
one-thousandth.
• In the metric system of
measurement, designations
of multiples and subdivisions
of any unit may be arrived at
by combining with the name
of the unit the prefixes on
the table.
Prefixes
Example:
1. 12x106 m
Answer:
1. 12 Mm
Example:
2. 314x10-3 m
Answer:
2. 314 mm
Significant Figures
• Also known as the significant digits or
precision of a number written in positional
notation are digits that carry meaningful
contributions to its measurement resolution.
Significant Figures Rules
All non-zero digits DO count.
24 = 2 digits
3.56 =
Leading zeros DON’T count.
(zeros in front of numbers)
0.421 = 3 digits
0.0025 =
Captive Zeros DO count.
(zeros between non-zero numbers)
1502 = 4 digits
1.008 =
Trailing Zeros DO count IF the number contains a DECIMAL.
(zeros at the end of numbers)
100 = 1 digit
206.0 = 4 digits
114.20 =
Expressing Numbers
• Numbers with more than three digits are
written in groups of three digits separated by
spaces
– Groups appear on both sides of the decimal point
• 10 000 instead of 10,000
• 3.141 592 65
Rounding off
• Rounding off is a type of estimation.
Estimation is used in everyday life and also in
subjects like Mathematics and Physics. Many
physical quantities like the amount of money,
distance covered, length measured, etc are
estimated by rounding off the actual number
to the nearest possible whole number.
Rounding Rules for Decimal
Numbers
Rounding rules for decimal numbers are as
follows:
• Determine the rounding digit and look at its
righthand side.
• If the digits at the righthand side are less than
5, consider them as equal to zero.
• If the digits at the righthand side are greater
than or equal to 5, then add +1 to that digit
and consider all other digits as zero.
Rounding Rules for Decimal
Numbers
Scientific Notation
• Is a way of expressing real numbers that are
too large or too small to be conveniently
written in decimal form. It may be refer to
scientific form or standard index form.
• This 10 base notation commonly used by
scientists, mathematicians, & engineers
impart because they can simplified certain
arithmetic operations.
Scientific Notation
Express the given numbers in
Scientific Notation
Convert the following numbers
into scientific notation:
1.
2.
3.
4.
5.
27 000 000
0.000 101
821
0.000 007 12
81 250 000 000
= 27 x 106
= 1.01 x 10-4
= 8.21 x 102
= 7.12 x 10-6
= 81.25 x 109