Physical Science

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Physical Science

• Chapter 1
• Boundaries and Measurements
• In Physical Science

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Physical science is the study of matter and
energy. A measurement must include both a
quantity and a unit. The metric system of
measurements was first used by France in 1799.
In 1960, the International System of Units (SI)
was formulated to bring the metric
system up-to-date. There are 7 SI base units and
combinations of these provide a variety of
derived units.
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Significant FiguresSignificant Digits
exact numbers found by counting defined
relationships inexact numbers measured values
Dot Right Not Left Rule
If there is a decimal (dot) in the number begin
counting digits from the right side and count
until the last non-zero digit. If there is no
decimal (dot) in the number begin counting digits
from the left side and count until the last
non-zero digit.
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Dimensional Analysis
Dimensional analysis is a method of converting
between units. A conversion factor represents a
unit equality. There are two ways to write a
conversion factor. Conversion factors are set up
so that units can cancel (numerator/denominator).
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Scientific NotationExponential Notation

• M x 10n

M is a number between 1 and 10 (having one digit
to the left of the decimal point) and n is an
integer. Determine M by moving the decimal point
in the original number to the left or the right
so that only one nonzero digit is to the left of
it. Determine n by counting the number of places
the decimal point has been moved. If moved to the
left, n is positive if moved to the right, n is
negative.
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Chapter 2

• Motion
• This chapter begins the study of a portion of
• physics referred to as mechanics.
• Mechanics is the study of motion and of the
  forces that cause motion.

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One of the first serious students of motion was
Aristotle (384-322 B.C.) He considered the
movement of objects in terms of their natural
motion.
Every object had a proper, or natural, place
where it should be. Aristotles theories did
not agree with physical observations and his
ideas were not supported by experimentation.

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Galileo Galilei (1564-1642) challenged Aristotles
science by performing experiments. Galileo
introduced the concept of time into the study of
physics.
Aristotle held that the most important feature in
determining the motion of an object was how far
away it was from its proper place. Galileo
recognized that it was the time of fall, or the
time for the motion to occur, that was an
important missing link.
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Speed is the distance an object moves divided by
the time required for the object to travel this
distance.
speed distance
time There are two
different types of speed average speed and
instantaneous speed. All physical quantities fit
into one of two categories vector quantities and
scalar quantities scalar quantity requires only
magnitude vector quantity has both magnitude and
direction
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Displacement and force are common physical
quantities that are vectors. Displacement is the
straight-line distance and direction from where
motion begins to where it ends. (triangle method
for vector addition) Speed and velocity are
terms that are often used interchangeably.
However, in physics the two have distinctly
different meanings. Speed is a scalar quantity,
whereas velocity is a vector quantity.
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Velocity is a vector quantity that requires a
knowledge of both magnitude and direction.
velocity displacement v d
time
t Acceleration is the change in velocity
of an object divided by the time it takes the
change in velocity to occur. acceleration
final velocity initial velocity a ?v
time
t If an object moving at
constant speed changes direction, the velocity
also changes. Starting, stopping, and turning are
all forms of acceleration.
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Acceleration Due to Gravity
Galileo proposed that all objects, heavy or
light, would fall with the same acceleration in
the absence of resistive forces. An object that
falls without any resistance to its motion is a
freely falling object. Acceleration varies
slightly at different locations. Measurements
show, however, that the acceleration due to
gravity is approximately 9.8 m/s2 everywhere on
Earth. velocity (9.8
m/s2)time
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Forces and Motion
Issac Newton (1642-1727 ) He is
considered by many to be the most brilliant
scientist who has ever lived.
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In scientific usage, the most commonly used unit
of force is the newton.
1N 0.224 lb resultant force or net force
the vector sum of all the forces acting on an
object
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The Pythagorean Theorem a2 b2 c2
R vA2 B2
This says that the length of the longest side R,
called the hypotenuse, is equal to the square
root of the sum of the squares of the lengths of
sides A and B. Forces fall into two
categories action-at-a-distance forces that one
object exerts on another even when there is no
physical contact between the two
(gravity) contact there is actual physical
contact between two or more objects
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Newtons First Law of MotionThe Law of Inertia

• A body at rest remains at rest, and a body in
  uniform motion in a straight line remains in such
  motion, unless acted upon by a net force.
• inertia the tendency for matter to remain in
  whatever state of motion that it is in
• mass how much inertia an object possesses
• weight force of attraction exerted by Earth

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Newtons Third Law of Motion

• For every force there is always an equal and
  opposite force.
• action/reaction pairs
• the forces are equal in magnitude
• they are opposite in direction
• they always act on different objects

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Newtons Second Lawof Motion

• The net force on an object equals the mass times
  its acceleration.
• Fnet ma
• Fnet is the net force on the object
• m is the mass
• a is the acceleration
• w mg

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Friction forces arise when one object attempts
to move across another. Frictional forces
always act in a direction that oppose
motion. Friction is reduced after rough objects
have been rubbed smooth or when lubricants are
used.
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Under the same conditions of temperature and
pressure, every substance has its own
characteristic density. density mass
d m
volume V Pressure is
defined as the force per unit area acting on a
surface. pressure force
P F area
A