# Physics The Science of Physics

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```					Physics Chapter 1, The Science of
Physics

From: Holt Physics, 2006
• Everything around us can be described by
using physics.
Areas within Physics
• *Mechanics: Studies motion and interactions
between objects.
• Examples: Falling objects, friction, weight,
spinning objects.
Mechanics
*Thermodynamics
• *Studies heat and temperature.
• Examples: melting and freezing processes,
engines, refrigerators.
*Vibrations and Waves
• *Deals with repetitive motions.
•            Examples: Springs, pendulums,
sound
*Optics
• *Studies Light
• Examples: Mirrors,
lenses, color, astronomy
*Electromagnetism
• *Deals with electricity, magnetism, and light
• Examples: Circuits, electronics
*Relativity
• *Studies particles that are moving at any
speed, even very high speeds
• Examples: traveling at high speeds, particle
accelerators, particle collisions.
*Quantum Mechanics
• *Studies the behavior of submicroscopic
particles.
• Examples: The atom and its parts
• Scientists use the Scientific Method to
investigate things.
• 1. Make observations and collect data that
• 2. Test Hypotheses by using experiments.
• 3. Interpret results, and revise the hypothesis
if necessary.
• 4. Make conclusions.

• *A Hypothesis is an explanation you make to
• Models are simplified representations that are
used to explain complex things.
• Many times a model is a diagram or a
computer simulation.
• Computer
Simulation
• A good physics model can predict what will
happen in new situations.
• If a model does not correctly predict what will
happen, it needs to be changed.
• A System is the specific things you want to
study. For example, studying the circuitry of a
TI-82 Calculator.
• A controlled experiment tests one factor at a
time.
• Controls are held constant in the experiment.
Create a fair race to see which animal, on
average, is faster over 100 m
Test different paint brushes to see
which works best.
Section 2, Measurements in
Experiments
• Dimension describes the kind of physical
quantity you are measuring.
• Three basic dimensions are length, mass, and
time.
• These three are used in different
combinations to describe many things like
force, velocity, energy, etc.
• How much of something you have is given by
Units. Like centimeters, kilometers, etc.
• SI is the standard measurement system for
science.
• Each unit is defined by a
standard, for example, a
“Meter is officially the distance light travels, in a
vacuum, in 1/299,792,458 seconds with time
measured by a cesium-133 atomic clock which
emits pulses of radiation at very rapid, regular
intervals.” from:
http://www.surveyhistory.org/the_standard_
meter1.htm
• Prefixes can be used in front of units to mean
powers of 10.
• Micro = 10-6, like a micrometer. This means
that there are 10-6 meters in a micrometer.
• Kilo = 103, This means that there are 1,000
grams in one kilogram.
Scientific Notation
• 1,400,000 =      1.4 x 10 6

• .00056   = 5.6 x 10 —4
Units Conversion:
• Use Conversion Factors to convert from one
unit to another.
• Conversion Factors are always equal to 1.
Like: 1 mm / 10-3 m = 1.
Or 106 m / 1 Megameter = 1.

See Table 3 in book.
Example, convert 7 mm to m.

Example 2: Convert 12.4 megameters to
centimeters.
• Convert 4 m3 to cm3:

• Convert 6,000 m3 to km3

• Convert 7 km/s2 to m/s2
*Accuracy and Precision
• *Accuracy: How close a measurement comes
to the correct value.
• *Precision: How close a series of
measurements are to one another. Or, how
exact a measurement can get, based on the
instrument you are using.
• Method error = An error caused by taking
some measurements with one process, and
using a different process to take other
measurements.

• Instrument error  Errors caused by faulty
equipment.
Determining Error of a measurement
• Error = [Experimental Value - Accepted Value]

• Percent Error = error / accepted value * 100%

• Example, you measured 120 cm, but it is 130
cm.
• Significant Figures: The digits in a
measurement that are known with certainty,
plus the first digit that is uncertain.
Non-Zero Numbers are always
significant.
• 236
Is a Zero a Significant Number or
Not?
•   Table 4 in book.
•   504
•   .006
•    50.0
•    7,000
Sig Figs in Calculations:
• Addition or subraction Round the final
answer to the last “shared column”.

• 13.4 + 5.234
Sig Figs in Calculations:
• Multiplication or Division The final answer
should have the same number of sig figs as
the measurement that had the least # of sig
figs.

• 1.50 x 2.0
• In this class, delay rounding until the very end.
• Tables and Graphs are important in Physics,
and any science.
• Physics Equations describe relationships.

• V = d/t

• F=m*a
• Symbols in equations: Delta, Sigma
• Table 8         F=m*a
On the Test: (What do the graphs
look like?)
• Y = mx + b

• Y = 2x + b

• Y=x+3
On the Test: (What do the graphs
look like?)
• Y = x^2

• Y = x^2 + 1

• Y = 3x^2

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