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UEQ: How do forces affect the motion of objects?
Day 1
Newton’s 1st and 2nd Law
†After
Attendance
(†EQ Sheet; Concept Map)
• Place HW on my desk
• †Pickup a new Essential Question Sheet and an
Effects of Force Concept Map
• Pickup and sign out your computer
• Log into www.plutonium-239.com
• Select the Warm-Up link
• Complete today’s warm-up and submit it
• Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
UEQ: How do forces affect the motion of objects?
Dynamics: Newton’s Laws
of Motion
UEQ: How do forces affect the motion of objects?
Review of Concept Map & Units of Chapter 4
• Force
• Newton’s First Law of Motion
• Mass
• Newton’s Second Law of Motion
• Newton’s Third Law of Motion
• Weight – the Force of Gravity; and the
Normal Force
UEQ: How do forces affect the motion of objects?
Units of Chapter 4
• Solving Problems with Newton’s Laws:
Free-Body Diagrams
• Applications Involving Friction, Inclines
• Problem Solving – A General Approach
UEQ: How do forces affect the motion of objects?
Equations to Know: Forces
F=ma
G=mg
f=N
Effects of Forces: Law of Inertia
EQ(s): How can forces be measured and quantified?
What are the defining characteristics of inertia?
Start: Why is it
more dangerous to
get hit by a car
than a snowball?
How can forces be measured and quantified?
What is a Force?
• According to Sir Alec Guiness:
QuickTime™ and a
decompressor
are needed to see this picture.
http://www.youtube.com/watch?v=ukbTFgQ4jxs
How can forces be quantified and measured?
4-1 Force
A force is a push or pull. An
object at rest needs a force
to get it moving; a moving
object needs a force to
change its velocity.
The magnitude of a
force can be measured
using a spring scale.
How can forces be quantified and measured?
4-1 Get To kNow All Forces
•
•
•
•
•
G: Gravity
T: Tension (ex. A tug-of-war rope)
N: Normal (ex. The floor below you)
A: Applied (ex. Pushing on a door)
F: Friction
How can forces be quantified and measured?
4-1 Get To kNow All Forces
•
•
•
•
•
Standing on the ground
Driving at a constant speed
Hitting T-ball
Tetherball
Walking
What are the defining characteristics of inertia?
4-2 Newton’s First Law of Motion
Newton’s first law is often called the law of
inertia.
Every object continues in its state of rest, or of
uniform velocity in a straight line, as long as no
net force acts on it.
What are the defining characteristics of inertia?
4-2 Newton’s First Law of Motion
Inertial reference frames:
An inertial reference frame is one in which
Newton’s first law is valid.
This excludes rotating and accelerating
frames.
What are the defining characteristics of inertia?
4-3 Mass
Mass is the measure of inertia of an object. In
the SI system, mass is measured in kilograms.
Mass is not weight:
Mass is a property of an object. Weight is the
force exerted on that object by gravity.
If you go to the moon, whose gravitational
acceleration is about 1/6 g, you will weigh much
less. Your mass, however, will be the same.
How can forces be measured and quantified?
What are the defining characteristics of inertia?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– What is the unit of mass?
– What is another name for Newton’s 1st Law?
– Which force is pushing up on you?
• HW (Write down in your Student Planner):
– No Homework
UEQ: How do forces affect the motion of objects?
Day 2
Newton’s 2nd Law
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
Newton’s 2nd Law
EQ(s): How can you infer the forces on an object from
information about its motion?
How can you use the summation of forces to calculate the
acceleration of an object?
Start: What
factors determine
the force of a
punch or kick?
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
POWER PUNCH
QuickTime™ and a
decompressor
are needed to see this picture.
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
4-4 Newton’s Second Law of Motion
Newton’s second law is the relation between
acceleration and force. Acceleration is
proportional to force and inversely proportional
to mass.
a
 F Fnet

m
m
(4-1)
 F(G,T,N,A,f )  ma
Cause = Effect
Invisible Forces  What We See
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
4-4 Newton’s Second Law of Motion
Force is a vector, so
each coordinate axis.
is true along
The unit of force in the SI
system is the newton (N).
Note that the pound is a
unit of force, not of mass,
and can therefore be
equated to newtons but
not to kilograms.
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
4-4 Newton’s Second Law of Motion
• When the net force is balanced, the
object does not accelerate.
• When the net force is unbalanced, the
object does accelerate.
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
Newton’s Second Law Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
WebAssign/Lab Time
• Work on WebAssign Problems 4.1 - 4.2 or Newton’s Second
Law - Constant Force Lab
• Final Copy Criteria
–
–
–
–
–
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
• Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
How can you infer the forces on an object from information about its motion?
How can you use the summation of forces to calculate the acceleration of an object?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– What is another name for the summation of forces?
– What part of Newton’s 2nd Law can we “see”?
– What forces comprise the summation of forces?
• HW (Write down in your Student Planner):
– Newton’s Second Law Lab (Questions and Conclusions)
– WebAssign Problems 4.1 - 4.2
UEQ: How do forces affect the motion of objects?
Day 3
Weight; Normal Force; Frictional
Force
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
Newton’s 3rd Law
EQ(s): What affects the strength of contact forces?
Start: Does the
kicker feel more
or less force than
the person being
kicked?
Life’s Essential Question:
What if it was this guy?
What affects the strength of contact forces?
4-5 Newton’s Third Law of Motion
Any time a force is exerted on an object, that
force is caused by another object.
Newton’s third law:
Whenever one object exerts a force on a second
object, the second exerts an equal force in the
opposite direction on the first.
What affects the strength of contact forces?
4-5 Newton’s Third Law of Motion
A key to the correct
application of the third
law is that the forces
are exerted on different
objects. Make sure you
don’t use them as if
they were acting on the
same object.
What affects the strength of contact forces?
4-6 Weight – the Force of Gravity;
and the Normal Force
Weight is the force exerted on an
object by gravity. Close to the
surface of the Earth, where the
gravitational force is nearly
constant, the weight is:
G  mg
What affects the strength of contact forces?
4-6 Weight – the Force of Gravity;
and the Normal Force
An object at rest must have no net force on it. If
it is sitting on a table, the force of gravity is still
there; what other force is there?
The force exerted perpendicular to a surface is
called the normal force. It is
exactly as large as needed
to balance the force from
the object (if the required
force gets too big,
something breaks!)
What affects the strength of contact forces?
4-8 Applications Involving Friction, Inclines
On a microscopic scale, most
surfaces are rough. The exact
details are not yet known, but
the force can be modeled in a
simple way.
For kinetic – sliding –
friction, we write:
or f  k N
is the coefficient
of kinetic friction, and
is different for every
pair of surfaces.
What affects the strength of contact forces?
4-8 Applications Involving Friction, Inclines
What affects the strength of contact forces?
4-8 Applications Involving Friction, Inclines
Static friction is the frictional force between two
surfaces that are not moving along each other.
Static friction keeps objects on inclines from
sliding, and keeps objects from moving when a
force is first applied.
or f  s N
What affects the strength of contact forces?
4-8 Applications Involving Friction, Inclines
The static frictional force increases as the applied
force increases, until it reaches its maximum.
Then the object starts to move, and the kinetic
frictional force takes over.
What affects the strength of contact forces?
Icy Intersection
QuickTime™ and a
decompressor
are needed to see this picture.
Watch the motion of the tires: Are they rotating? Why
is this important to understanding their motion?
What affects the strength of contact forces?
Newton’s 2nd Law - Constant Force Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
What affects the strength of contact forces?
WebAssign/Lab Time
• Work on WebAssign Problems 4.3 - 4.5 or Newton’s Second
Law - Constant Force Lab
• Final Copy Criteria
–
–
–
–
–
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
• Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
What affects the strength of contact forces?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– What is the formula used to calculate weight?
– The force of gravity pull on an object is also known as ________.
– What is the formula for the force of friction?
• HW (Write down in your Student Planner):
– Newton’s Second Law - Constant Force Lab (Questions and
Conclusions)
– WebAssign Problems 4.3 - 4.5
UEQ: How do forces affect the motion of objects?
Day 4
Free Body Diagrams;
Inclined Planes;
Problem Solving
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
Free Body Diagrams
EQ(s): How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on
an object?
Start: What forces
are acting on the
person being
kicked?
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
4-7 Solving Problems with Newton’s Laws –
Free-Body Diagrams
1. Draw a sketch.
2. For one object, draw a free-body
diagram, showing all the forces acting
on the object. Make the magnitudes
and directions as accurate as you
can. Label each force. If there are
multiple objects, draw a separate
diagram for each one.
3. Resolve vectors into components.
4. Apply Newton’s second law to each
component.
5. Solve.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
4-7 Solving Problems with Newton’s Laws –
Free-Body Diagrams
When a cord or rope pulls on
an object, it is said to be under
tension, and the force it exerts
is called a tension force.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
4-8 Applications Involving Friction, Inclines
An object sliding down an incline has three forces acting
on it: the normal force, gravity, and the frictional force.
• The normal force is always perpendicular to the surface.
• The friction force is parallel to it.
• The gravitational force points down.
If the object is at rest,
the forces are the same
except that we use the
static frictional force,
and the sum of the
forces is zero.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
4-9 Problem Solving – A General Approach
1. Read the problem carefully; then read it again.
2. Draw a sketch, and then a free-body diagram.
3. Choose a convenient coordinate system.
4. List the known and unknown quantities; find relationships
between the knowns and the unknowns.
5. Estimate the answer.
6. Solve the problem without putting in any numbers
(algebraically); once you are satisfied, put the numbers in.
7. Keep track of dimensions.
8. Make sure your answer is reasonable.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Newton’s 2nd Law - Constant Force Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
WebAssign/Lab Time
• Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second
Law - Constant Force Lab
• Final Copy Criteria
–
–
–
–
–
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
• Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– Draw a FBD for m1. (3 Forces)
– Draw a FBD for m2. (2 Forces)
– Write the individual Fx for m1.
• HW (Write down in your Student Planner):
– Newton’s Second Law - Constant Force Lab (Questions and
Conclusions)
– WebAssign Problems 4.1 - 4.22
UEQ: How do forces affect the motion of objects?
Day 5
Work Day
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Newton’s 2nd Law - Constant Force Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
WebAssign/Lab Time
• Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second
Law - Constant Force Lab
• Final Copy Criteria
–
–
–
–
–
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
• Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– Not Applicable
• HW:
– Newton’s Second Law - Constant Force Lab (Questions and
Conclusions)
– WebAssign Problems 4.1 - 4.22
UEQ: How do forces affect the motion of objects?
Day 6
Work Day #2
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Newton’s 2nd Law - Constant Force Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
WebAssign/Lab Time
• Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second
Law - Constant Force Lab
• Final Copy Criteria
–
–
–
–
–
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
• Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
How do you use vectors to draw a free body diagram?
How do you use a free body diagram to determine the net force on an object?
Summary
• Answer the Essential Questions.
• Ticket out the Door:
– Not Applicable
• HW:
– Newton’s Second Law - Constant Force Lab (Questions and
Conclusions)
– WebAssign Problems 4.1 - 4.22
Day 7
Summary/Work Day
After Attendance
•
•
•
•
•
•
Place HW on my desk
Pickup and sign out your computer
Log into www.plutonium-239.com
Select the Warm-Up link
Complete today’s warm-up and submit it
Logout and return the computer to the cart
Feed Back for Google Docs
• Was anything confusing on google docs?
• Noteworthy Student Responses
UEQ: How do forces affect the motion of objects?
Summary of the Effects of Force
• Newton’s first law: If the net force on an object
is zero, it will remain either at rest or moving in
a straight line at constant speed.
• Newton’s second law:
• Newton’s third law:
• Weight is the gravitational force on an object.
• The frictional force can be written:
(kinetic friction) or
(static friction)
• Free-body diagrams are essential for problemsolving
UEQ: How do forces affect the motion of objects?
†Effects of Force Essential Questions
• What are the defining characteristics of inertia?
• How can forces be quantified and measured?
• How can you use the summation of forces to calculate the
acceleration of an object?
• How can you infer the forces on an object from information about
its motion?
• What affects the strength of the contact forces?
• How do you use vectors to draw a free body diagram?
• How do you use a free body diagram to determine the summation
of forces on an object?
†Answer these before the test.
UEQ: How do forces affect the motion of objects?
Newton’s 2nd Law - Constant Force Lab
• Work in groups of no more than 4 people.
• Return all supplies to the counter/cart.
UEQ: How do forces affect the motion of objects?
†EQ/WebAssign/Lab
Time
•
†Answer the Essential Questions
•
Work on WebAssign Problems 4.1 - 4.22 or Newton’s Second Law Constant Force Lab
•
Final Copy Criteria
–
–
–
–
–
•
State the problem (Ex. Find displacement)
Draw a picture/diagram
Provide a list or table of all given data (Ex. t = 2 s)
Solve the problem symbolically (Ex. v=x/t  x = vt)
Plug in numbers and units to obtain answer.
(Ex. x = (5 m/s)(2 s)= 10 m)
Notes about WebAssign:
– Positive vs. negative answers (Try a negative sign)
– Look at the final unit (hours or minutes or seconds)
UEQ: How do forces affect the motion of objects?
Summary
• Ticket out the Door:
Write down two questions and their answer for the test tomorrow and
turn it in.
– One conceptual problem
– One mathematical problem
• HW (Write down in your Student Planner):
– Answer the Essential Questions
– Newton’s Second Law - Constant Force Lab (Questions and
Conclusions)
– WebAssign Problems 4.1 - 4.22
– WebAssign Final Copy
Day 8: Test
Effects of Force
UEQ: How do forces affect the motion of objects?
†After
Attendance
•
Place HW on my desk (in Reverse Alphabetical Order):
WebAssign Final Copy
Essential Questions
Laboratory Assignment(s)
•
Pickup the following:
Chapter 5 Vocabulary Acceleration
Scantron Sheet
•
Fill in the following on the scantron sheet front:
Name: Write your name on it!!
Subject: PIM
Test: EOF
Date: S10
Period: Block 2
UEQ: How do forces affect the motion of objects?
†Effects of Force Test
• Do not write on Part I (the scantron questions)
• Put your name on Part II and complete it
• Verify any corrections below that have made before submitting
your test.
• Complete the Chapter 5 Vocabulary Acceleration
Test Corrections
• Question
UEQ: How do forces affect the motion of objects?
Summary
• Ticket out the Door:
Turn in the Effects of Force Test
• HW:
– Chapter 5 Vocabulary Acceleration
4-5 Newton’s Third Law of Motion
Rocket propulsion can also be explained using
Newton’s third law: hot gases from combustion
spew out of the tail of the rocket at high speeds.
The reaction force is what propels the rocket.
Note that the
rocket does not
need anything to
“push” against.
4-5 Newton’s Third Law of Motion
Helpful notation: the first subscript is the object
that the force is being exerted on; the second is
the source.
This need not be
done indefinitely, but
is a good idea until
you get used to
dealing with these
forces.
(4-2)