Chapter 1
Principle of physics
Measurement
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
What is physics
- A way of describing the physical world
- understanding the behavior and structure of matter
- deals with how and why matter and energy act as they do
- Evaluate explanations of physical phenomena
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
Fundamental Quantities (Basic Quantities)
• quantities cannot be measured in a simpler form And for
convenience they have been selected as the basic quantities.
• quantities that cannot be defined in any other physical
quantity. Some
Some quantities
The units of these are called Derived Units
cannot
Some quantities cannot be measured in a
simpler form and for convenience they have
• The units of these quantities are called basic Units.
Some quantities they have been selected as
the
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
Table System International (SI) base quantities
basic quantities
quantity
Unit
Symbol
length
meter
m
mass
kilogram
kg
time
second
s
electric current
ampere
A
thermodynamic temperature
kelvin
K
amount of substance
mole
mol
candela
cd
luminous intensity or (Unit of intensity of light)
Quantities Physics
Fundamental Quantities (Basic Quantities)
•The three main fundamental physical
quantities (base
quantities) of mechanics are length, mass and time .
•The SI system have the units meter (m) , kilogram (kg) , and
second (S).
• These fundamental quantities cannot be defined in terms of
more base quantities .
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
Fundamental unit (Basic unit)
• The Meter :- the distance traveled by a beam of light in a vacuum
over a defined time interval ( 1/299 792 458 seconds)
• The Kilogram :- a particular platinum-iridium cylinder kept in
Sevres, France
• The Second :- the time interval between the vibrations in the
cesium atom (1 sec = time for 9 192 631 770 vibrations)
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
Fundamental unit (Basic unit)
Exercise : (Homework) (SI)
The Unit of Length is ………..
The Unit of Time is ………..
The Unit of Electric Current is ………..
The Unit of Temperature is ………..
The Unit of a mount of Substance is ………..
The Unit of Mass is ………..
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
Derived Quantities:
• All physical quantities measured by physicists can be expressed in
terms of the three basic unit of length, mass, and time .
• When a quantity involves the measurement of 2 or more
fundamental quantities it is called a Derived Quantity.
• The units of these are called Derived Units.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Quantities Physics
© 2014 John Wiley & Sons, Inc. All rights reserved.
SYSTEM OF UNIT

SI units (used mostly in physics):
length: meter (m)
mass: kilogram (kg)
time: second (s)



#This system is also referred to as the MKS system for meter-kilogramsecond.
© 2014 John Wiley & Sons, Inc. All rights reserved.
SYSTEM OF UNIT
Gaussian units (used mostly in chemistry):
•
length: centimeter (cm) cm = 0.01 m
•
mass: gram (g)
g= 0.001 kg
•
time: second (s)
# This system is also referred to as the CGS system for centimeter-gramsecond.
© 2014 John Wiley & Sons, Inc. All rights reserved.
SYSTEM OF UNIT
British engineering system (FPS)
length: foot (ft)
ft = 0.30 m
mass: bound
bt= 0.45 kg
time: second (s)
# its easy to convert from system to another .

•
•
•
© 2014 John Wiley & Sons, Inc. All rights reserved.
CONVERSIONS
• You will need to be able to convert from one unit to another for the
same quantity
Km to m (length)
J to eV (energy)
Years to seconds (time)
And between other systems and SI
**Note: throughout you should be able to do basic conversions now and
others will be developed
© 2014 John Wiley & Sons, Inc. All rights reserved.
CONVERSIONS
*
1 km = 1000 m (meters)
1kg = 1000 g
1 mile=1609 m
1g
= 0.001 kg
1 mile = 1.609km
1cm = 0.01 m
1 inch = 2.54 cm
1 min = 60 s
1 cm = 0.39 inch
1 hr = 3600 s
1 m3 = 1000 L
© 2014 John Wiley & Sons, Inc. All rights reserved.
CONVERSIONS
Example : Convert 3 cm to …….inch ?
Example : Convert 6 inch to ………cm ?
Example : Convert 1mile to ……km ?
Example : Convert 19 km to ………mile ?
Example : Convert 5 mile/hr to ………. m/s ?
Example : Convert 7 m/s to ………. mile/min ?
Example : Convert 2 hrs to ………. s ?
Example : Convert 4 min ………. hrs ?
© 2014 John Wiley & Sons, Inc. All rights reserved.
Scientific notation

Scientific notation employs powers of 10 to write large or
small numbers
Example :
Convert the number to scientific notation
#
897000
= (
)
#
0.000584
=(
)
* What is the difference between the two numbers
-
(4.34 x104 m , 43.4 x 103 m )
-
(0.003 x 10-4 s , 0.00003 x10-6 s)
-
Power of ten prefixes :
Prefix
Symbol
Prefix
Symbol
X=18
exa
E
deci
d
15
peta
P
-2
centi
c
12
tera
T
-3
milli
m
9
giga
G
-6
micro
6
mega
M
-9
nano
n
3
kilo
K
-12
pico
p
2
hecto
h
-15
femto
f
1
deca
da
-18
atto
a
© 2014 John Wiley & Sons, Inc. All rights reserved.