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Chapter 1 Physics and Measurement

الكلية كلية التربية للعلوم الصرفة     القسم قسم الفيزياء     المرحلة 1
أستاذ المادة فؤاد عطية مجيد       06/03/2019 12:39:06
We have always been curious about the world around us.
Classical Physics – It constructs the concepts Galileo (1564-1642) and Newton’s
space and time. It includes mechanics (rotation), light, heat (James Joule, Sadi Carnot),
sound, electricity and magnetism (James Maxwell)
Modern Physics – The application of special relativity, and particularly quantum
theory, to such microscopic systems as atoms, molecules, and nuclei, which has led to
a detailed understanding of solids, liquids, and gases, is often referred to as modern
physics.
Recording / Measurement – Compare with a standard length, mass, or time
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1.1 Standard of Length, Mass, and Time
The International System of Units:
SI system: meter, kilogram, second
Appendix A (The English System)
1 inch = 2.54 cm, 1 ft = 30.48 cm
1 mi = 1.609 km
1 lb = 0.454 kgw
1 atm = 14.7 lb/in.2 (PSI) = 760 mmHg = 101325 Pa (N/m2) ~ 1 kgw/cm2
The English system of
measurement grew out of the
creative way that people measured for
themselves. Familiar objects and parts
of the body were used as measuring
devices. For example, people measured
shorter distances on the ground with their
feet.
Length:
Distance traveled by light in a vacuum
during a time of 1/299 792 458 second.
Give the correct length measurement for the
left and the right rulers.
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Time:
Atomic clock: 9 192 631 770 times the period of oscillation of radiation from the
cesium-133 atom.
Scientists have manufactured the world s smallest atomic clock, with
inner machinery about the size of a grain of rice. Requiring very little
power to run, the device loses only one second every 300 years and
could one day provide precise timekeeping for portable applications
such as wireless communication devices and Global Positioning
System (GPS) receivers. Like other atomic clocks, the new design
relies on the natural vibrations of cesium atoms, which “tick” 9.2
billion times each second. John Kitching of the National Institute of
Standards and Technology and his colleagues trapped cesium vapor
inside a chamber that is probed by a tiny laser, resulting in two
electromagnetic fields. The team then adjusted the fields until the
difference between them equaled that of the energy levels within the
cesium atoms, causing the atoms to stop absorbing or emitting light.
An external oscillator was then stabilized against the natural
resonance frequency of cesium. “The real power of our technique is
that we re able to run the clock on so little electrical power that it could be battery operated and that it s small
enough to be easily incorporated into a cell phone or some other kind of handheld device”, explains Kitching.
“And nothing else like it even comes close as far as being mass producible.”
Mass:
Kilogram is defined as the mass of a specified platinum-iridium alloy cylinder kept at
the International Bureau of Weights and Measures at Sevres, France.
Radio Controlled Exact Set Atomic Projection, Alarm and Wall
Clocks from Oregon Scientific, Casio, La Crosse Technology
and more.
Radio controlled clocks or "Atomic Clocks" keep perfect time by
automatically synchronizing to the radio signal emitted from the
U.S. Atomic Clock in Colorado. Radio controled clocks reset
daily to the split second, and adjust automatically to Daylight
Savings Time, Leap Year and Time Zone Changes.
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You Must Know:
Length:
Mean radius of Earth: 6400 km, 6.4 x 106 m
Diameter of a hydrogen atom: 10-10 m, r = 0.529 angs
Diameter of a proton: 10-15 m
Mass:
Human: 7 x 101 kg
Hydrogen atom: 1 * 10-3 / 6.02 * 1023 = 1.67 * 10-27 kg
Time:
One day: 8.64 * 104
10-18: atto
10-15: femto
10-12: pico
10-9: nano
10-6: micro
10-3: mili
103: kilo
106: mega
109: giga
1012: tera
1015: peta
Density and Atom Mass
Density: ? = m / V
Gold: 19.3 * 103 kg / m3 = 19.3 g / cm3
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Lead: 11.3 * 103 kg / m3 = 11.3 g / cm3
Copper: 8.93 * 103 kg / m3 = 8.93 g / cm3
Aluminum: 2.7 * 103 kg / m3 = 2.7 g / cm3
Example: A solid cube of aluminum has a volume of 0.200 cm3. It is known that 27.0
g of aluminum contains 6.02 * 1023 atoms. How many atoms are contained in the
cube?
1.2 Matter and Model Building
Quarks: up, down, strange, charmed, bottom, and top
You should develop a process of building models as you study physics.
1.3 Dimensional Analysis
vf = vi + at
v has a dimension of L / T
a has a dimension of L / T2
Quantity Symbol Dimension
Area A L2
Volume V L3
Speed v L/T
Acceleration a L/T2
Force f ML/T2
Pressure p M/LT2
Density d M/L3
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1. Express the number in scientific notation, with the multiplier of the power of ten
between 1 and 10.
2. If the multiplier is less than 10 = 3.162 (the square root of ten), the order of
magnitude of the number is the power of ten in the scientific notation. If the
multiplier is greater than 3.162, the order of magnitude is one larger than the
power of ten in the scientific notation.
102 ´103 = 100´1000 =100000 =105
= 6.02´1023 A N
Example: In 12g of carbon, there are A N carbon atoms. If you could count 1 atom
per second, how long (in years) would it take to count the atoms in 1 g of carbon?
6.02´1023 /12/1(atom/ s) /86400/365 = 1.59´1015
0.0086 ~ 10-2
1.6 Significant Figures
The significant figures include the first estimated digit.
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Rule: multiplication & division – The number of significant figures in the result of
multiplication or division is no greater than the least number of significant figures in
any of the factors.
2.00 * 6.10 = 12.2
2.00 * 6.112 = 12.2
2.00 * 6.1 = 12
Rule: addition & subtraction – The result of addition or subtraction of two numbers
has no significant figures beyond the last decimal place where both of the original
numbers had significant figures.
1.001 + 0.003 = 1.004
1.001 + 0.2 = 1.201=1.2
Measurement
Number of
Significant Digits
Distance between Markings on
Measuring Device
142.7 g 4 1 g
103 nm 3 10 nm
2.99798 x 108 m 6 0.0001 x 108 m
Example: A rectangle has a length of 3.21±0.02 m and a width of 2.8±0.1 m. Please
calculate the area.

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