Download Acceleration - Solon City Schools

Motion Unit
Chapter 10
1
Measuring Motion
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Motion is the change in
an object’s position.
Reference point is a
stationary object that is
used to compare an
object’s motion.
Displacement is the
change in position of an
object.
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Straight line.
Must be in a particular
direction.
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Speed
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Speed is how fast an object
moves.
v=d÷t
Common unit for measuring
speed is m/s
 distance
 time
Speed is illustrated in a
distance-time graph.
 Time on the x-axis
 Distance on the y-axis
 Horizontal line indicates
that the object is not
moving.
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Types of Speed
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Constant speed is speed
that does not change.
Average speed is the
distance traveled by an
object divided by the
time the object takes to
travel that distance.
Instantaneous speed is
speed measured in an
infinitely small time
interval.
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Velocity
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Velocity is speed and
direction.
 Common unit for
velocity is m/s north
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distance
time
direction
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Acceleration
Chapter 10, section 2.
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Acceleration is the rate at which
velocity changes over time

Speed changes
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Increasing
Decreasing
Direction changes

If you travel in a
circle at a
constant speed,
you’re
accelerating
because you are
constantly
changing
directions.
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Centripetal Acceleration

Centripetal acceleration is
the acceleration that occurs
in uniform circular motion
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Calculating Acceleration
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acceleration = vfinalvinitial/time or a = v/t
Small acceleration,
velocity is increasing
very gradually
Large acceleration,
velocity is increasing
more rapidly
Positive acceleration
always means a the
object’s velocity is
always increasing
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Negative Acceleration

Negative acceleration
means the object’s velocity
is decreasing
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Graphing acceleration
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Plot the time on the
x-axis
Plot the velocity on
the y-axis
A straight line
indicates positive
acceleration
Positive slope
represents speeding
up
Negative slope
represents slowing
down
Slope is zero if the
acceleration is zero
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Balanced and unbalanced forces
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A force is an action exerted on
a body in order to change the
body’s state of rest or motion
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A force has a magnitude and
direction
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The net force is the
combination of all of the forces
acting on the object
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The object accelerates
in the direction of the
net force.
The object will not
accelerate if the net
force is zero.
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Balanced and unbalanced forces
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Balance forces do not
cause an object at rest to
start moving

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Net forces are zero
Unbalanced forces cause
the object to move in the
direction of the greater
force

Net forces are greater
than zero
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Force of friction
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Friction is a force that opposes
motion between two surfaces
that are in contact
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The rougher the surface, the
greater the friction

Static friction is the force
that resists the initiation of
sliding motion between two
surfaces that are in contact
and at rest
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Force of friction
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Kinetic friction is the force
that opposes the movement
of two surfaces that are in
contact and are sliding over
each other

Sliding friction occurs
when objects pass each
other

Rolling friction occurs
when a round object
rolls over a flat surface
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Force of friction

Static friction is usually greater
than kinetic friction
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Fluid friction is the friction
between air and the surface of
the moving object
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Air is displaced as an
object moves
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Air resistance increases as
the speed of the object
increases
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Designing a shape of a
car to displace less air
is called streamlining
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Friction and motion
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Friction is necessary, but
sometimes harmful
Friction can be reduced by
lubricants
Friction can be increased
by making surfaces rougher
Hydroplaning occurs when
water is trapped between
the tires of a car and the
road.
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Review Questions
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What do you call a stationary object that is used for a comparison
to detect motion?
 (reference point or reference frame)
What do you call the distance between the starting point to the
final destination?
 (displacement)
What describes how fast an object moves?
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What is the type of speed when equal distances are covered in
equal time?
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(constant speed)
What is graphed on the x-axis of a speed graph?
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(speed)
(time)
What is graphed on the y-axis of a speed graph?
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(distance)
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Review Questions
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What do you call the total distance the object traveled divided by
the total time it took for the object to move that distance?
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What is speed measured in infinitely small time intervals?
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(v = d/t)
What is the formula for calculating acceleration?
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(velocity)
What is the formula for calculating speed?
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(instantaneous speed)
What do you call speed with direction?
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(average speed)
(a = (vf –vi)/t
What do we call the rate in change of velocity?
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(acceleration)
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Review Questions
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What do we graph on the y-axis of an acceleration graph?
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What type of forces causes change in motion of an object?
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(a push or pull)
What do we call the force that resist a surface moving over
another surface?
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(balanced forces)
What is a force?
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(unbalanced forces)
What type of forces causes no change in the motion of an object?
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(speed)
(friction)
What is the type of friction where everything is stationary?
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(static friction)
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Review Questions
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What type of friction involve moving objects?
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What are the two types of kinetic friction?
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(sliding friction & rolling friction)
What type of friction is air resistance?
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(kinetic friction)
(fluid friction)
What reduces friction?
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(lubricants)
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Review Questions
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Review Questions
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Review Questions
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