Transcript Forces and Motion

Forces and Motion Content
Competency Goal 4:
The learner will conduct investigations and use
appropriate technologies to build an
understanding of forces and motion in
technological designs.
Alex Richardson
Elementary Science Coach
[email protected]
1
Background Concepts
The motion of an object can be described by
its position , direction of motion, and speed.
The study of motion and forces that cause
motion should provide concrete experiences
for students.
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Background Concepts (cont.)
Students understand descriptions of moving
objects and begin to describe forces acting
on objects when simple objects are used.
Force can be treated as the originator of
motion. However, fundamental forces of
nature should have an emphasis on
gravitational force.
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Background Concepts (cont.)
The Earth’s gravity pulls on any object toward
it without touching it.
Gravitational force is an attraction between
masses.
The strength of the force is proportional to the
masses and weakens rapidly with increasing
distance between them.
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Background Concepts (cont.)
Changes in speed or direction of motion are
caused by forces.
The greater the force is, the greater the change
in motion will be.
The more massive an object is, the less effect
a given force will have.
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Background Concepts (cont.)
How fast things move differs greatly.
Some things are so slow that their journey
takes a long time.
Other things move too fast for people even to
see.
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Background Concepts (cont.)
Integration of the concepts of forces and
motion will increase student understanding.
Measuring, graphing, and simple statistics are
appropriate math connections.
Technology integration can be achieved
through collecting data and providing
evidence.
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Background Concepts (cont.)
Social Studies integration can be achieved
through exposing students to the historical
development of the theories and laws used
to explain forces and motion.
Read and discuss biographical literature
concerning the scientists responsible for the
development of theories and laws to
integrate Language Arts.
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Background Concepts (cont.)
Enrich learning for all students with forces
and motion using nonfiction literature,
fiction literature, and creative writing.
Art and physical education can be used to
assess student learning in certain activities
in forces and motion.
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Objective: 4.01 Determine the motion of an object by
following and measuring its position over time.
Many variables can affect motion such as:
gravity, speed, time and direction.
A variable is anything that can change in an
experiment.
Gravity is a force of attraction that exists
between all objects.
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Gravitational Concepts (cont.)
The force of gravity depends on the masses
of two objects and the distance between
them. (The Law of Universal Gravitation)
Gravitational force between two objects is
greater when their masses are large.
The Earth’s mass is extremely large. As a
result, the force of gravity between Earth
and objects on Earth is very strong.
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Speed and Time Concepts
The measure of how fast an object moves is
its speed.
Speed measures the distance an object
travels in a specific amount of time.
In order to find an object’s speed, take the
distance and divide it by the time.
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Speed and Time Concepts (cont.)
Speed can be measured using a stopwatch
and a meter stick.
Velocity is the speed of an object in a
particular direction.
The velocity of an object changes if either
its speed or its direction of travel changes.
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Direction Concepts
Direction is measured with a compass.
The points on a compass are N for North, S
for South, E for East, and W for West.
To describe an object’s velocity, you must
include both its speed and the direction it is
moving.
You must use a stopwatch, a meter stick,
and a compass to measure velocity.
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Change in motion is observed or measured
in reference to something else.
Changes in speed or direction of motion are
caused by force.
Objects not in motion will continue in that
state until acted upon by some force.
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Objects in motion will continue along a
straight line at a constant speed unless acted
upon by some force.
The way to change how something is
moving is to give it a push or a pull.
When more than one force acts upon an
object , the forces may reinforce each other
or cancel each other out.
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Principles of Force and Motion
Can be
Objects not Objects set
observed in acted upon in motion
everyday
by force
by force
actions
Objects in
motion
affected by
time
Object’s
motion
affected by
direction
Objects in
motion with
the effect of
forces
canceling
each other out
Object’s
motion
affected by
speed
Objects in
motion with
forces
reinforcing
each other
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Newton’s First Law of Motion
This first law is often called the law of
inertia.
An object at rest remains at rest unless acted
on by an unbalanced force.
An object in motion continues to move at a
constant speed in a straight line unless acted
on by an unbalanced force.
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Inertia
The tendency of an object to resist a change
in its motion.
Is Related to Mass
Objects with more mass have more inertia.
Objects with less mass have less inertia.
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Newton’s Second Law of Motion
The greater the unbalanced force acting on
an object , the greater the acceleration of the
object.
Applying an unbalanced force to a smaller
mass will produce a greater acceleration on
the object than the same force applied to a
larger mass.
Force is inversely proportional to mass.
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Newton’s Third Law of Motion
This law is often called the law of action and
reaction.
Forces come in pairs.
Whenever one object exerts a force on a second
object, the second object exerts a force on the first
object that is equal in magnitude and opposite in
direction.
Action/reaction force pairs don’t always cause
motion.
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Momentum
Momentum is an example of Newton’s third
law of motion.
Momentum is a measure of how hard it is to
stop a moving object.
The momentum of a moving object depends
on its mass and velocity.
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Momentum (cont.)
As mass and velocity increase, so does
momentum.
Action and reaction forces result in momentum
being transferred from one object to another when
objects collide.
One object may gain momentum while another
loses momentum.
The total amount of momentum remains the same
in every collision.
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Objective: 4.02 Evaluate how pushing or pulling forces can
change the position and motion of an object.
Force is pushing or pulling of an object that
results in a change in motion.
Force is one of the measures of the
relationship between objects.
Force is action on an object that causes its
momentum to change.
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Force acting on an object in motion will
speed it up, slow it down, or change its
direction.
Force can cause an object at rest to start
moving.
Forces that push or pull can result in a
change in direction or speed of a motion.
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Forces can work together or against each
other.
Balance and unbalance in pulling and
pushing can change the direction of the
object and or the quality of the motion such
as fast, slow, and etc.
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Objective: 4.03 Explain how energy is needed to make
machines move. (moving air and gravity).
The sun is the primary source of all energy.
Energy moves from one source to another.
Energy cycles through living as well as
nonliving things.
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Energy is needed to make machines move
or make machines operational.
Air movement and gravity are two forces
that cause motion to occur.
Energy is never created nor destroyed.
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Each form of energy can be converted.
It simply changes from one form to another.
All forms of energy may be either potential
or kinetic.
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Potential energy is stored energy.
The higher above ground an object is and
the greater its mass, the more potential
energy it has.
Kinetic energy is energy associated with
motion.
The faster an object moves and the greater
its mass, the more kinetic energy it has.
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Energy is found in many forms.
AC HELMS is a mnemonic that will help
A - Atomic
capture the forms of energy.
C - Chemical
H - Heat
E - Electricity
L - Light
M - Motion
S - Sound
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Objective: 4.04 Determine that an unbalanced force is
needed to move an object or change its direction.
Forces that are not equal and opposite are
unbalanced.
Force includes any push or pull that results
in the motion of an object.
An unbalanced force influences the objects
movement.
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Unbalanced Forces (cont.)
An unbalanced force causes an object to
change its speed of an object already in
motion.
An unbalanced force is the exertion of more
force from one direction than from other
directions.
An unbalanced force causes an object to be
set in motion or change its direction.
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Unbalanced Forces (cont.)
An object can have more than one force
acting on it.
If the sum of all forces acting on an object
are unbalanced, they can make objects at
rest start moving, or moving objects change
their direction or speed.
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Balanced Forces
Balanced forces are equal and opposite.
Balanced forces cancel each other out, so
motion does not change.
If an object is at rest , it will remain at rest.
It it is in motion, it will remain in motion.
If any forces acting on an object are
balanced, the net force is zero.
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Objective: 4.05 Determine factors that affect motion
including: Force, Friction, Inertia, and Momentum.
Force is the pulling or pushing that results
in a change in the motion, size, or shape of
an object.
Friction is a force that creates resistance in
the motion of two surfaces rolling, rubbing,
sliding, pulling or pushing against each
other.
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Friction
Friction works against motion.
Friction is produced when two objects come
in contact with each other.
The amount of friction two objects produce
depends on how rough the objects are.
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Friction (cont.)
If the objects are rough, they produce more
friction as they rub against each other.
If the objects are smooth, they produce less
friction as they rub against each other.
Friction depends on how hard two objects
are pushing against each other.
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Inertia and Momentum
Please review Objective: 4.01 Determine
the motion of an object by following and
measuring its position over time.
Review content concepts 19, 22, and 23.
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Objective: 4.06 Build and use a model to solve a
mechanical design problem. Devise a test for the model.
Evaluate the results of test.
Problems and solutions can be identified.
Designing solutions may also have
constraints and barriers that need to be
resolved.
Suitable tools and technologies need to be
used to reach a successful outcome.
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Many design processes are used to come up
with a solution to a problem.
Design requirements specify how a product
must perform.
Engineers develop, modify, and improve
designs to meet specific requirements of a
product.
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Solutions should be identified for their
effectiveness in responding to the problem.
Solutions to a problem may be
accomplished by modifying something that
already exists.
Appropriate tools are used to help make
better decisions based on observation,
measurements, and ease of work.
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Various ways to demonstrate the
effectiveness or drawbacks of a solution
Design a computer model to predict what
would happen in different situations.
Perform a demonstration to see how the
design works and record observations.
Use previously collected data on the design
such as written observations, drawings, and
class discussions.
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Objective: 4.07 Determine how people use
simple machines to solve problems.
Machines range from simple to complex.
A simple machine is a tool that makes work
easier.
A complex machine is made up of simple
machines.
The use of machines are reflected in every
aspect of our lives and on a daily basis.
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The greater the force and the greater the
distance the object moves, the more work is
done.
Work happens when a force moves an
object through a distance.
Work equals force times distance: W= F x d
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Machines are used in reducing the amount
of effort needed to complete a task.
Most simple machines let you use less force
to move an object.
When you use less force, you have to apply
it for a longer distance.
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Some simple machines let you move an object a
longer distance. You have to apply more force ,
but you can apply it for a shorter distance.
With any kind of simple machine, the amount of
work you do doesn’t change.
What changes is the amount of force you apply
and the distance you apply it.
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Six Basic Kinds of Simple Machines
Inclined plane
Wedge
Screw
Lever
Wheel and axle
Pulley
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Inclined Plane
An inclined plane can reduce the amount of
force needed to move a heavy object.
An inclined plane is a flat surface that
slopes.
You apply less force, but you have to apply
it for a longer distance.
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Wedge
A wedge can reduce the amount of force
needed to split apart objects.
A wedge is an incline plane that moves.
You have to apply force for a longer
distance when you use a wedge.
A wedge moves the object’s pieces a short
distance.
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Screw
A screw can reduce the amount of force needed to
fasten two objects together.
A screw is an inclined plane wrapped around a
small rod.
The inclined plane forms ridges on the screw.
You use less force to turn the screw, but you have
to apply the force for a longer distance.
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Lever
A lever can reduce the amount of force
needed to raise heavy objects off the
ground.
A lever is a long bar or board that turns
around a support that doesn’t move. The
support is called the fulcrum.
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Three Kinds of Levers
The fulcrum is between the object you are
moving and the force you are applying.
The object you are moving is between the
fulcrum and the force you are applying.
You apply force between the fulcrum and
the object you are moving.
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Wheel and Axle
A wheel and axle can reduce the amount of
force or the distance you apply the force.
A wheel and axle is a wheel that turns
around a rod, called the axle.
The axle goes through the center of a wheel.
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Pulley
A pulley can be used to change the direction
of a force, or reduce the amount of force
needed to lift a heavy object.
A pulley is a wheel with a rope or chain
wrapped around it
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Three Kinds of Pulleys
A pulley changes the direction of the force you
apply. You pull down , and the object moves up.
The pulley does not reduce the amount of force
that you have to apply.
A pulley reduces the amount of force that you
have to apply. Some of the weight is held by the
object that the rope is attached to. Therefore, you
don’t pull as hard. The pulley doesn’t change the
direction of the force. You pull up, and the object
moves up.
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Three Kinds of Pulleys (cont.)
A block and tackle pulley system is a
combination of other two kinds of pulleys.
Using more than one pulley reduces the
force that is needed to lift the object.
You have to pull the rope a longer distance
when you use this system.
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