Monday,
November 18, 2013
H Physics
Standards: 1c Newton’s 2nd Law of
Motion
Warm Up
A ball travels 50 meters to
the west in 20 seconds. Find
the speed of the ball. Find
the velocity of the ball.
Objective SWBAT draw free body
diagrams
Agenda:
1. Warm Up
2. P.2 Review Graphing Worksheet
3. P.2 Work on Problem Solving
4. P.4 Free Body Diagram Inquiry
Homework
Study Worksheets for Test P.2
P.4 Homework #FH6
P.2 Test Tomorrow: Study the 2
Bootcamp Worksheets
Tuesday,
November 19, 2013
H Physics
Standards: 1c Newton’s 2nd Law of
Motion
Objective: SWBAT create free body
diagrams.
Agenda
1. Warm Up
2. P.2 Take Test
3. P.4 Free Body
Diagram MiniLecture
4. Force Stations:
Elaborate Section
Warm Up
Draw a free body diagram
of a skydiver in free-fall while
s/he is still speeding up.
Homework
#FH6
Wednesday,
November 20, 2013
H Physics
Standards: 1c Newton’s 2nd Law of Motion
Warm Up
p.2 Draw a diagram for the following
scenario: A cart rolls across a table
with an applied Force of 10N, a
frictional force of 5N, no air
resistance, and a mass of 2kg. It’s
acceleration is unknown.
p.4 Draw a free body diagram of the
above scenario.
Learning Objective: SWBAT create free
body diagrams.
Agenda:
1. Warm Up
2. P.2 Finish Exam
3. P.2 Begin Force Stations Lab
4. P.4 Finish Force Stations Lab
5. P.4 Practice Free Body Diagrams
Homework
#FH6
P.4 Finish Force Stations Lab
Thursday,
November 21, 2013
H Physics
Warm Up
Draw a Free Body Diagram
for a car skidding to a stop.
Standards: : 1c Newton’s 2nd Law of Motion
Learning Objective: SWBAT solve problems
using Free Body Diagrams
Agenda
1. Warm Up
2. P.2 Force Stations
3. P.4 Collect Force Stations Lab
4. P.4Free Body Diagram Problem Solving
Guided Practice
5. P.4Practice #FH7
Homework
#FH7 P.4
Quiz Friday – Free Body
Diagrams P.2
#FH6 P.2
Friday ,
November 22, 2013
H Physics
Standards:
1c Newton’s 2nd Law
Objective; SWBAT will score 80% on the
quiz.
Agenda:
1. Warm Up
2. P.4 Quiz 6
3. P#4 Introduce #FH8 Free Body
Diagram Problem Solving
4. P.2 Force Stations Lab
5. P.2 Guided Practice Free Body
Diagrams
Warm Up
Create a free body diagram
of a car driving down a hill
where friction & air
resistance will affect the
car’s motion.
Homework
P.2 #FH7
P.4 #FH8
Symbols, units and
equations Study Guide
Equations:
Constant Velocity
v=
Dx
Dt
d
v
=
Dy = y f - yi s t
Dx = x f - xi
Constant Acceleration
Dv
a=
Dt
The Two equations of Motion
1.
v f = vi + at
2.
1
Dx = vi t + at 2
2
Dy = y f - yi
Dx = x f - xi
The Two equations of Motion
for Falling Objects
ag=-9.8m/s2
v f = vi + agt
1
Dy = vi t + agt 2
2
Forces
Symbol
Units
t
s
v
m/s
a
m/s2
F
kgm/s2 or N
Δx
m
Fnety = F1y + F2 y + F3y +...Fny
Fnetx = F1x + F2 x + F3x +...Fnx
Fnety = F1y + F2 y + F3y +...Fny
Fnet = ma
Fg = W = mg
Types of Forces
• From your book p. 94 Table 4-2
Force
Symbol
Definition
Direction
Friction
Ff
Resistive Force. Comes
from rubbing against or
sliding across surfaces.
Parallel to the surface and
opposite the direction of
sliding
Normal
FN
The force exerted on an
object by the ground, a
table, a platform, or any
surface.
Perpendicular to and away
from the surface.
Spring
Fsp
Restoring Force. The push
or pull a spring exerts on
an object.
Opposite the
displacements of the object
at the end of the spring.
Tension
FT
The pull exerted by a
string, rope, or cable when
attached to something.
Away from the object and
parallel to the string, rope,
or cable at the pont of
attachment.
Thrust, Applied Force
Fthrust,Fap
A general term for the
forces that move objects
such as rockets, planes,
cars and people.
In the same direction as
the acceleration of the
object.
Weight
Fg
Attractive Force of two
objects due to gravity.
Usually Earth and and
object
Straight down towards the
center of the earth.
Air Resistance/Drag
FAR
Resistive Force, comes
from air/wind hitting
moving objects
Opposite of Motion
Modeling the Graphing
Process
Step One – label each axis with the symbol and the units
being represented by the graph.
1st column x-axis, 2nd column y axis
Step Two – Create your x and y axis scales. To create a
scale(your numbering system on the graph) look at your
smallest and largest data points. Then pick a number
sequence (ex. 1,2,3,4 or 2,4,6,8) that will allow all of the
points to fit on your graph.
Step Three – Plot the Points.
Step Four – Make a best fine line. It has to be straight and
you need to make it go through the center or through the
average of your points. See board for more explanation.
Step Five – Find the slope of the graph.
Step Six (Honors Only) – Find the equation of the graph by
substituting your data into the formula y=mx+b
Force Stations
•
•
•
•
•
Objective: Gain an introduction to free-body diagrams (FBDs), and create accurate FBDs of
physical systems at stations around room.
Engage
Watch discovery channel video clip on the physics of skydiving (~3 min.):
http:/www.youtube.com/watch?v=ur40O6nQHsw .
Explore
Students rotate around force stations in the room and explore each system ~16 min
o
o
•
•
•
•
•
•
•
•
For the full 10 pts of credit requires full completion of explore,
explain, elaborate, and evaluate sections. Evaluate is Homework
worth 10 points.
Identify the Labeled Station
Explore each station: 2 minutes, identify all the forces acting on the object, and draw all the forces on the object.
1. Object at rest on table
2. Cart rolling across table
3. Object hanging by string
4. Object hanging by two strings at an angle to each other
5. Ball rolling down ramp
6. Object stationary on ramp
7. Ball falling through air
8. Coffee filters falling through air
Explain
Mini-lecture on FBDs (Free Body Diagrams) ~5 min
Students revise any force station FBD that is incorrect.
Students finish guided practice problem.
Elaborate
Using magazines provided in class, cut out a picture that shows an interesting physical
scenario. Then students create FBD for one or multiple objects in the cutout picture.
Evaluate
“Free-Body Exercises: Linear Motion” #F6
HW: #FH6
After you create each free
body diagram, use your free
body diagram to make an
Fnet=ma equation in the x
direction and in the y
direction like we did during
the Explain portion of the
lesson.
Ex
FAR FF
FN
``
FAP
``
Fg
Fnetx=Fap-Ff-FAR=macar-x-direction
Fnety=FN-Fg=macar y-direction
Free Body Diagrams
What are they? – These are diagrams similar to the
one’s we are used to drawing, but with one major
exception. You only put Forces on them.
FN
Why do we make them?
1. They help us solve problems
involving multiple forces.
2. Looking at the diagram to the
right. Fnetx=Fap-Ff-FAR
Fnety=FN-Fg
FAR
FAP
FF
` `
When do we make them?
Remember Fnet=ma? You
create a free body diagram Fnetx=Fap-Ff-FAR=macar-x-direction
to help you find the Fnet
Fnety=FN-Fg=macar y-direction
portion of this equation.
` `
Fg
Question: If the car has a
2000 kg mass, its applied
force is 10,000 N, friction is
1500 N, and Air Resistance is
1000 N, find the car’s
acceleration and the *Normal
Force acting on the car?
Free Body Diagrams #FH7
For each problem:
a. Draw a Free Body Diagram of the problem.
b. Make an equation for Net Force in the x (horizontal) and y
(vertical) directions.
c. Then plug in the numbers and Calculate the net force in the x
direction and then the y direction.
d. Find ax and ay
1. A man pushes a 5kg box with 15 N force to the right
while it encounters a 10 N friction force.
2. An 1kg egg is free-falling from a nest in a tree. Neglect
air resistance.
3. A 2kg flying squirrel is gliding (no flapping wings) from
a tree to the ground constant velocity.
4. A rightward force of 10 N is applied to a 1kg book in
order to move it across a desk. Consider a frictional force
of 4 N.
5. A 50kg gymnast is suspended motionless from the
ceiling by a bar and two vertical ropes, each with a 25 N
Problem Solving using FBD’s #F8
1. If a car’s engine accelerates the car using 50,000 N of
Force. Friction is resisting the motion with 12,000 N. Find
the acceleration of the 2000kg car?
2. If a 60kg skydiver is freefalling towards the ground, and
the air resistance half way to the ground is 500 N. What
is the net force on the skydiver?
3. From Problem 2, what is the acceleration of the
skydiver?
4. If a 70 kg skydiver is freefalling at terminal velocity, what
is the air resistance that the free faller is experiencing.
5. If a 1200 kg car’s engine applies 50,000 N to accelerate
the car and it achieves a 2.5m/s2 acceleration, how
much friction is acting on the car? (Assume air
resistance is negligible.)
6. If a 20 kg slab of wood is being accelerated on ice at
1.25 m/s2 and friction is small at 5 N. What is the applied
force on the slab of wood?