Download Motion

9/13 BELL WORK
 What can you catch but not throw?
Hint: Over winter break I caught a _____. It was horrible!
9/13 SCHEDULE
 Finish Measurement Test and turn in (15 -20 minutes)
 Notes 11 .1 “Observing Motion”
 Observe motion
Assignments:
UNIT : MOTION
EVERYBODY’S DOING
THE LOCOMOTION…
Objectives:
1. Describe force and motion.
2. Analyze relationship between force and motion
3. Calculate rates of change (velocity and acceleration).
Ch 11
WHAT IS MOTION?
 Based on the pictures below, what do you think motion is?
 Can you figure out which way the people are moving? How
CH 11.1 : MEASURING MOTION
Objectives
1. Use a frame of reference to describe motion.
2. Distinguish between speed and velocity.
3. Create and use graphs to study speed.
MEASUREMENT DEVICES
How do you measure motion?
• Measure distance, or how far something goes.
• Measure time, or how long a motion takes.
• Measure speed, or how fast something is moving.
Each of the devices shown below can be used to measure
some aspect of motion.
DEVICES, CONTINUED
1. Do these devices measure distance, time, or speed?
2. What units are possible for a measurement: meters (m),
seconds (s), or meters per second (m/s)?
OBSERVING MOTION
When an object changes position with respect
to a frame of reference, the object is in motion.
 frame of reference: a system for determining the exact
location of objects in space and time
 multiple FoR possible, and can seem to contradict each other.
 Is the girl in the train moving?
OBSERVING MOTION, CONTINUED
Distance vs Displacement
 Distance measures the path taken.
• Displacement is the change of an object’s position.
•ALWAYS includes direction.
• In the diagram:
– Distance = yellow
line
– Displacement =
black arrow
OBSERVING MOTION, CONTINUED
Examples…
 Earth travels about 583
million miles around the
sun every year.
 Distance = 583 mil mi
 Displacement = 0 mi
Where should you be at
this time tomorrow?
 Distance = travel around
school, home, and back
 Displacement = 0 mi
REVIEW
 Frame of Reference is similar to point of view.
 Defined by place and time
 Can contradict each other/ have different answers.
 Distance vs Displacement
 Distance measures path.
 Displacement measures change in relative position and MUST include
a direction.
SPEED AND VELOCIT Y
Speed vs. velocity
〉Speed = how fast an object moves.
〉Velocity = the speed and the direction that
the object moves.
Example
 speed: 75 mph
 velocity: 75 mph east on I-10
SPEED AND VELOCIT Y, CONTINUED
Velocity is described relative to a reference point.
 Direction is described as positive or negative along the
line of motion.
 Up and right are usually positive, and left and down are
negative.
The canon has negative
velocity.
The cannonball has
positive velocity.
SPEED AND VELOCIT Y, CONTINUED
Combined velocities determine
the resultant velocity.
 Speed is ALWAYS positive,
velocity can be + or -.
Example
 Plane flies 500 km/h with a 100
km/h tailwind.
 Plane appears to be going…
 500 km/h in the plane,
 600 km/h on the ground.
9/14 BELL WORK
 What gets wetter and wetter the more it dries?
9/14 SCHEDULE
 Notes 11 .1 “Observing Motion”
 Domino Speed Lab
 Collect data today, start on questions
Assignments:
MARBLE OBSERVATIONS – 20 MINUTES
Need 5 marbles and a ruler.
 Use a pencil/pen like a pool cue to make 1 marble hit the
other 4 like the diagram. “Shoot” the marble 3 times from
each position.
 How does where the marble hit af fect the others?
 Compare the speed of the shooter with the others.
 Why is the shooter usually larger than the other marbles?
2
1
MARBLE OBSERVATIONS – 20 MINUTES
Need 5 marbles and a ruler.
 Use a pencil/pen like a pool cue to make 1 marble hit the
other 4 like the diagram. “Shoot” the marble 3 times from
each position.
 Record distance the 4 marbles in the center traveled in a
labeled chart. Find the average.
30 cm
2
30 cm
1
MARBLE OBSERVATIONS
Questions:
 Did the 4 marbles react the same every time they were
struck? Why?
 The “shooter” marble travelled 30 cm. Did the other marbles
move the same/more/ less distance? Why do you think this
is?
 How could you make the marbles take a curved path?
CALCULATING SPEED
Average speed is calculated as distance divided by time.
distance
d
speed =
, or v =
time
t
• Metric unit for speed: meters per second (m/s)
• constant speed: equal distances in equal amounts
of time
• instantaneous speed: the speed at a given time
MATH SKILLS
Velocity
Metal stakes are sometimes placed in glaciers to help
measure glacial movement. For several days in 1936,
Alaska’s Black Rapids glacier surged as swiftly as 89
meters per day down the valley. Find the glacier ’s velocity
in m/s. Remember to include direction.
1. List the given and the unknown values.
time, t = 1 day
distance, d = 89 m down the valley
velocity, v = ? (m/s and direction)
MATH SKILLS, CONTINUED
2a. Perform any necessary conversions.
To find the velocity in meters per second, the value for
time must be in seconds.
distance
d
speed =
, or v =
time
t
t = 86 400 s = 8.64 x 10 4 s
MATH SKILLS, CONTINUED
2b. Write the equation for speed.
distance
d
speed =
, or v =
time
t
3. Insert the known values into the equation, and solve.
d
89 m
v= =
(For velocity, include direction.)
4
t 8.64 ´ 10 s
v = 1.0 ´ 10-3 m/s down the valley
GRAPHING MOTION
• Motion can be studied using a distance vs. time graph.
– time (x-axis) = independent variable
– distance (y-axis) = dependent variable
• The slope of a distance vs. time graph equals speed.
GRAPHING SKILLS
Calculating Slope
Remember slope is change in y /
change in x.
Or - - (y 2 -y 1 ) / (x 2 -x 1 )
Rise/run
GRAPHING SKILLS, CONTINUED
1 . Choose two points that you will
use to calculate the slope.
Point 1: t = 1 s and d = 6 m
Point 2: t = 4 s and d = 12 m
2. Calculate the vertical change
and the horizontal change.
ver tical change = 12 m – 6 m
= 6m
horizontal change = 4 s – 1 s =
3 s
GRAPHING SKILLS, CONTINUED
3. Divide the vertical change by
the horizontal change.
slope = 6 m /3 s = 2 m/s
9/15 BELL WORK
Don’t use a calculator. Careful on the
exponent.
379.1 x 10 -4 = ?
9/15 SCHEDULE
 Set up charts and graphs for Your Speed Lab
 Finish Domino Speed Lab – Turn in
Assignments:
1. Domino Speed Lab due TODAY
MEASURING YOUR SPEED LAB
 Materials




Meter stick
Stopwatch
Calculator
Masking tape
 Determine the average time for 4 people in your group to walk
and jog 6 m and then 12 m.
 Set up charts to collect data and graphs today. Also include
places to calculate your group’s 4 average speeds.
9/16 BELL WORK
A typist increased her speed from 60 words per minute to
75 wpm.
 What percent did her speed increase?
9/16 SCHEDULE
 Your Speed Lab
 Turn Domino Speed Lab – LATE
Assignments:
1. Domino Speed Lab LATE
MEASURING YOUR SPEED LAB
 Materials




Meter stick
Stopwatch
Calculator
Masking tape
 Determine the average time for 4 people in your group to walk
and jog 6 m and then 12 m.
 Set up charts to collect data and graphs today. Also include
places to calculate your group’s 4 average speeds.
9/19 BELL WORK
Sid Shady is in prison planning his escape. The cell
is 3 x 3 x 3 meters. The walls are reinforced
concrete and extend 2 m below the dirt floor. The
only openings are a locked door and a skylight. Sid
has a plan and starts digging. He can’t tunnel out,
but it’s crucial to his plan.
 How does he hope to escape?
9/19 SCHEDULE




Velocity Practice Problems in notebooks
Notes Ch 11 .2 “Acceleration”
Finish Your Speed Lab – due TODAY
Velocity and Acceleration Calculations - WED
Assignments:
1. Domino Speed Lab LATE
2. Your Speed Lab – TODAY
3. Velocity and Acceleration Calc sheet - WEDNESDAY
VELOCIT Y PROBLEMS
1 . What was the equation for speed?
2. Elroy rides the bus every day to school. He's sure that the bus
driver is driving too fast, and one day they're going to get pulled
over. He rides the bus 12 miles to FTHS and it takes about 9
minutes.
Figure out their average speed in mph. Should he be worried?
VELOCIT Y PROBLEMS
Solve the problems in your notebook. Draw a simple diagram of
the situation.
1 . If Steve throws a football 50 m in 3 s, find the speed of the
ball.
2. Bart ran 5000 m from the cops at an average speed of 6 m/s
before they finally tackled and cuf fed him. How long did he run
in minutes?
3. Mike rode his motorcycle 20 m/s for 500 s. How far did he
go?
CH 11.2 “ACCELERATION”
〉Describe what happens as objects accelerate.
〉Calculate straight-line acceleration.
〉Use a graph to find acceleration.
VELOCIT Y REVIEW
Velocity involves changes in speed or direction.
1 . Which of the following are changing velocity? Briefly
explain.
a. a car coming to a stop at a stop sign
b. a book sitting on a desk
c. a yo-yo in motion
d. a bicyclist making a left -hand turn at exactly 15 km/h
VELOCIT Y REVIEW
2. If the box wasn’t moving, will its velocity increase or stay the
same? In which direction (if any) will the velocity be after the
student pulls on the rope?
ACCELERATION AND MOTION
Acceleration = velocity changes = change in
speed, direction, or both
ACCELERATION AND MOTION,
CONTINUED
Acceleration can be a change in speed.
 An increase OR decrease in speed is an acceleration.
 Slowing down becomes negative acceleration.
ACCELERATION AND MOTION,
CONTINUED
Acceleration can also be a change in
direction.
 A motorcyclist who rides around the inside
of a large barrel is constantly accelerating.
 A person riding a Ferris wheel is
accelerating.
 Acceleration in a circular motion is
centripetal acceleration.
CALCULATING ACCELERATION
〉The average acceleration over a given time can be found by
dividing the change in the velocity by the time.
〉The formula for straight-line acceleration is…
average acceleration =
a =
v f - vi
t
v
=
t
final velocity - initial velocity
time
CALCULATING ACCELERATION,
CONTINUED
Acceleration is the rate at which velocity changes.
 + a = velocity increasing—> object is speeding
up.
 - a = velocity decreasing—> object is slowing
down.
 SI units of acceleration = meters per second per
second (m/s/s), or m/s 2
MATH SKILLS
Acceleration
A flowerpot falls of f a second-story windowsill. The flowerpot
starts from rest and hits the sidewalk 1 .5 s later with a
velocity of 14.7 m/s. Find the average acceleration of the
flowerpot.
1 . List the given and the unknown values.
Given:
time, t = 1.5 s
v i = 0 m/s
vf = 14.7 m/s down
Unknown: acceleration, a = ? (m/s 2 and direction)
MATH SKILLS, CONTINUED
2. Write the equation for acceleration.
final velocity – initial velocity vf – v i
acceleration =
=
time
t
3. Insert the known values into the equation, and solve.
a=
v f - vi
t
14.7 m/s - 0 m/s
=
1.5 s
14.7 m/s
a=
= 9.8 m/s2 down
1.5 s
YOUR SPEED LAB
 Determine the average times for walking 6 m and 12 m,
jogging 6 m and 12 m.
 Graph your data (time is the independent variable)
Analysis Questions:
1 . Are your group’s average walking times for 6m and 12 m
consistent? Why or why not.
2. Are your group’s average jogging times consistent?
3. What are some sources of error in this lab?
9/20 BELL WORK
Which verb past tense does not belong with the others? Why?








bring
fight
buy
seek
catch
teach
draw
think
9/20 SCHEDULE
 Notes Ch 11 .2 “Acceleration”
 Reaction Time Lab
 Work time
 Velocity and Acceleration Calculations - WED
Assignments:
1. Domino Speed Lab LATE
2. Your Speed Lab – LATE
3. Velocity and Acceleration Calc sheet - WEDNESDAY
ACCELERATION PRACTICE PROBLEMS
Be sure to include units!!
1 . What is the equation for acceleration?
2. A turtle swimming straight towards shore has a speed of
0.50 m/s. After 4.0 s, its speed is 0.80 m/s. What is its average
acceleration?
ACCELERATION PRACTICE PROBLEMS
3. Mai's car accelerates at an average rate of 2.6 m/s 2 . How
long will it take her car to speed up from 24.6 m/s to 26.8
m/s?
REVIEW VELOCIT Y AND ACCELERATION
 Are these objects changing velocity?
 Are they accelerating?
 Why?
GRAPHING ACCELERATED MOTION
The slope of a straight line on a speed vs. time
graph is equal to the acceleration.
GRAPHING ACCELERATED MOTION,
CONTINUED
Acceleration can also
be seen on a distance
vs. time graph.
– Straight lines mean no
change in velocity, not
accelerating
–Curved lines mean the
object is changing velocity
and accelerating
GRAPHING SKILLS
Graphing Acceleration
A bus traveling on a straight road at 20 m/s uniformly
slows to a stop over 20 s. The bus remains stopped for
20 s, then accelerates at a rate of 1 .5 m/s 2 for
10 s,
and then continues at a constant speed. Graph speed vs.
time for 60 s. What is the bus ’s final speed?
1 . Determine the x-axis and the y-axis of your graph.
The x-axis will indicate time, t, measured in s. The yaxis will indicate speed, v, measured in m/s.
GRAPHING SKILLS, CONTINUED
2. Starting from the origin, graph each section of the
motion.
A. Draw and connect the first two
points:
t = 0 s, v = 20 m/s
t = 20 s, v = 0 m/s
B. Draw a horizontal line from t = 20
s to t = 40 s at v = 0 m/s.
C. Starting at t = 40 s and v = 0
m/s, draw a line with a slope of
1.5 m/s2.
D. Draw a horizontal line from t = 50
s to t = 60 s at v = 15 m/s.
GRAPHING SKILLS, CONTINUED
3. Read the graph to find the final speed.
At time t = 60 s, the speed
is 15 m/s.
9/21 BELL WORK
Shadow was examining a 14 ½ degree angle using his
magnifying glass that makes things 2 times bigger.
Under the glass, how large would the angle measure?
9/21 SCHEDULE
 Review notes Ch 11 .2 “Acceleration”
 Reaction Time Lab
 Work time
 Velocity and Acceleration Calculations - WED
Assignments:
1. Domino Speed Lab LATE
2. Your Speed Lab – LATE
3. Velocity and Acceleration Calc sheet - WEDNESDAY
VELOCIT Y, DISTANCE, TIME, AND
ACCELERATION ID
Sort the following words into the correct category:
- meters
- m/s
Quantity
- seconds
time
- meters per s 2
- how long
speed
- how far
- acceleration
- v
distance
- t
- d
acceleration
- a
GRAPHING ACCEL PRACTICE
Be sure to include units!! Use the graph paper
6. When graphing speed and time, which axis is the speed and
which is time? Which is the dependent variable?
7. A car accelerates from a stop at a rate of 2 m/s 2 for 20 s,
then continues at a constant speed for 40 s. Graph the speed
vs. time of the car.
a. What is the slope between 0 and 20 s? _______________
b. What is the slope of the line between 20 and 60 s?
___________________
c. What car's speed at 10 s? What is the final speed?
GRAPHING ACCEL PRACTICE
Be sure to include units!! Use the graph paper
8. A train traveling at 30 m/s takes 60 seconds to slow to a
complete stop. Graph the speed vs. time of the train for 80 s.
a. What is the slope of the graph at 30 s?
b. What is the slope of the line at 75 s? Is the train accelerating at this
point? Why?
MIXED VELOCIT Y & ACCELERATION
PROBLEMS
1 . What are the equations to find speed and acceleration? What
units are usually used?
2. Cheetahs at top speed can run 274 m in 8.65 s. Find the top
speed.
 Is 274 m a distance, speed, time, or acceleration?
 Is 8.65 s a distance, speed, time or acceleration?
 Which equation should you use?
MIXED VELOCIT Y & ACCELERATION
PROBLEMS
3. A plane flys 100 km/hr with respect to the air. If there is a
25 km/hr tailwind, how fast would the plane seem to be going
to a person on the ground?
4. Japanese Shinkansen trains travel up to 186 miles per hour.
Kai walks 3.1 mph towards the back of a train going at top
speed. What is his relative speed?
5. A dog running 1 .5 m/s skids to a stop with an acceleration of
-0.35 m/s 2 . How long did it take to stop?
CH 11.3 “MOTION AND FORCE”
Objectives:
〉Identify and describe the 4 fundamental
forces.
〉Explain the effects of a net force on an
object.
〉Analyze the causes and effects of friction.
INTRO FORCES
 What keeps the following objects in place?
 Why do these objects eventually hit the ground?
INTRO FORCES
 Why do these objects keep moving? How can you stop them?
FUNDAMENTAL FORCES
4 fundamental forces affect motion.
〉Strong nuclear force, weak nuclear force,
gravity, and electromagnetic force.
〉Any other forces are linked back to these.
FUNDAMENTAL FORCES
Nuclear Forces – ONLY short distances
 Strong nuclear force holds protons and neutrons
together.
 Weak nuclear force is mostly radioactive decay.
FUNDAMENTAL FORCES
Gravity: attraction between any 2 objects
Electromagnetic Force: caused by magnetism,
electric fields, and charged particles
 10 36 x Earth’s gravity
 Friction is a result of the electromagnetic force.
There is often more than one
force on an object.
Little friction + gravity = ouch!
FUNDAMENTAL FORCES, CONTINUED
Fundamental forces vary in strength and distance at
which they act.
 Contact vs Field Forces
 Contact Forces – objects must touch
 Push, pull, slide, roll, etc
FUNDAMENTAL FORCES, CONTINUED
 Contact vs Field Forces
 Field forces do not require that the objects touch
 Gravity, magnetism, electrostatic force…
 Both contact and field forces can cause an object to
move or to stop moving.
Iron moves, no strings attached.
Contact force = air
resistance
Field force = gravity
BALANCED AND UNBALANCED FORCES
Effect of 2 or more forces
〉Balanced forces = motion does not change
〉Unbalanced forces = accelerates in the direction
of the net force.
 net force: the combination of all forces acting on an object
She doesn’t move until
she applies additional
force to the ground.
BALANCED & UNBALANCED FORCES,
Balanced forces do not change motion.
 Forces are balanced when the net force is zero.
 Ex: For a light hanging from the ceiling (at rest), the
upward force due to tension in the cord balances the
downward force of gravity.
Floating in the Dead Sea…
gravity down = buoyant force up
BALANCED AND UNBALANCED FORCES IN
ACTION
Demonstrate Balanced v. Unbalanced Forces
 Pair up, stand with feet close together, hold each other’s
wrist, and lean apart.




What forces do you feel?
Are forces balanced?
What could cause forces to become unbalanced?
What would happen to you if this happened?
10/5 BELL WORK
Read’em and Reap wants to give away coloring books. They’ve
created a puzzle, so they don’t have to give away too many.
 The first week of a month without an A in it.
 On a day of the week with a U in it.
 The month has no E, but the day does.
When will they give away the coloring books?
10/5 SCHEDULE
 Notes Ch 11 .3 “Motion and Force”
 Force diagrams in packet
ALL assignments so far MUST be in
by TUESDAY at 3:30 pm for credit!
Assignments:
1. Velocity and Acceleration Practice LATE
2. Acceleration Lab LATE
3. Letter Home - LATE
VELOCIT Y AND ACCEL REVIEW PROBS
 What distance will you travel if you are going 120km/ hr for
30. min? Watch your units!
 What is the acceleration of a bike that goes from 38 km/ hr to
a stop in 4.5 s?
BALANCED AND UNBALANCED FORCES IN
ACTION
Force Diagrams show forces acting on an object.
1. Drawing that represents object
2. Labeled arrows showing forces
3. Units are usually N (newtons)
 Use your text book to help you explore force diagrams.
 Push on it according to the arrows, and see what happens.
Which way will the ball go?
75 N
75 N
BALANCED AND UNBALANCED FORCES IN
ACTION
Force Diagrams show forces acting on an object.
1. Drawing that represents object
2. Labeled arrows showing forces
Math with forces
1. Same direction, add
2. Dif ferent direction, subtract
Which way will the ball go?
75 N
75 N
BALANCED AND UNBALANCED FORCES IN
ACTION
What forces are acting on the stationary block?
 Gravity (points down)
 Weight of the block vs. Friction (Friction greater since block
isn’t moving)
 Normal force (perpendicular to surface)
BALANCED & UNBALANCED FORCES
Unbalanced forces do not cancel completely.
 The object will accelerate towards the net
force.
 Ex: If you push a box east and your friend
pushes the box north, the box will accelerate
FCB less than FL
in a northeasterly direction.
REVIEW FORCE DIAGRAMS
Draw force diagrams for the following situations:
 A football is falling after being kicked by the punter.
 Ignore air resistance
 A backpack is hanging by one strap from your shoulder.
 Two students are dragging a couch across the room to the
right.
REVIEW FORCE DIAGRAMS
Force Diagrams
 Use a box or dot to represent the object
 Arrows show direction and relative size of
forces.
Common Considerations and Abbreviations
 gravity: usually down, F g or F grav
 friction: oppose motion, F frict
 Friction moving through air = F
air resistance
 normal: perpendicular to surface contact,
F N or F normal
 applied: push, pull, etc.. F app
 Things rising through air or water F buoyancy
10/6 BELL WORK
Gravity on Mars is one-seventh what it is on Earth.
 How much do you weigh on Earth? How much would
you weigh on Mars?
10/6 SCHEDULE
 Practice Force Diagrams
 Notes Ch 11 .3 “Motion and Force”
 Friction Lab
ALL assignments so far MUST be in
by TUESDAY at 3:30 pm for credit!
Assignments:
1. Velocity and Acceleration Practice LATE
2. Acceleration Lab LATE
3. Letter Home - LATE
PRACTICE FORCE DIAGRAMS
Draw the force diagrams for these situations.
 Object on the floor slows due to friction.
 Light fixture is dangling from the ceiling.
 Car is being winched uphill.
THE FORCE OF FRICTION
Friction always opposes the motion when two
surfaces are in contact.
Results…HEAT!!
Friction fire-starting
THE FORCE OF FRICTION
Static friction is greater than kinetic friction.
 static friction: the force that resists the initiation of
sliding motion between two surfaces that are in contact
and at rest
 kinetic friction: the force that opposes the movement of
two surfaces that are in contact and moving over each
other.
No kinetic friction until he starts to move.
THE FORCE OF FRICTION
Ex: Is it more difficult to get the couch moving, or
keep it moving?
THE FORCE OF FRICTION
Types of kinetic friction
 sliding friction: objects slide past
each other
 rolling friction: rounded object rolls
over a flat surface
 in general, rolling friction < sliding
friction
FRICTION AND MOTION
Friction is necessary for many everyday tasks
to work correctly.
FRICTION AND MOTION
Unwanted friction can be lowered.
 using low-friction materials, such as nonstick
coatings on cooking pans
 lubricants, such as motor oil, wax, and grease
FRICTION AND MOTION
Helpful friction can be increased.
 scattering sand on icy roads to keep cars from
skidding
 wearing textured batting gloves
 wearing cleats to get traction on wet grass
FRICTION AND MOTION
10/7 BELL WORK
Two mothers and two daughters go shopping. They
have 21 $1 bills which they split so each got $7.
 How is this possible?
10/7 SCHEDULE
 Practice Force Diagrams
 Friction Lab Pt 1-2
Ch 11 “Motion” test TUESDAY
Assignments:
PRACTICE FORCE DIAGRAMS
Draw Force Diagrams for the following situations.
 A hot air balloon is tethered down to keep it from rising.
 Skier heads downhill. Consider friction and air resistance.
10/8 BELL WORK
A utopia is a perfect/ideal/wonderful place. What would you
need in a utopia? Why?
10/8 SCHEDULE
 Get Textbooks
 Work time
 Finish Friction Lab – DUE TODAY
 Finish Force Diagrams packet – DUE TODAY
 Cross off on back pg: #6-7, 14, 19
 “Motion” Ch 11 Review due TUESDAY
Ch 11 “Motion” test TUESDAY
Assignments:
1. Friction Lab due TODAY
2. Force Diagrams packet due TODAY
3. Motion Review due TUESDAY
10/13 BELL WORK
Even if they are starving, natives living in the Artic don’t harvest
penguin eggs. Why not?
Penguin Distribution
10/13 SCHEDULE
 Friction Labs?
 7 min to study and ask specific questions on material
 Ch 11 “Motion” test
 Use paper notes and calculator
Assignments:
1. Friction Lab LATE
2. Force Diagrams packet LATE
3. Motion Review due TODAY
FRICTION AND MOTION DEMO
 Friction is a REACTION force.
 Pushing the desk _____________ results in a ____________
friction force.
 When you stop pushing, friction _____________.
 What kind of friction stops the chair from moving?
BLOCK FRICTION
 Find the mass of the wooden block. Convert it to kg.
 Find maximum angle before the block slides to the end of the
meter stick.
 Record the time needed to slide 1 m.
 You can calculate the force of the moving block using F = ma.
Choose the most useful form of the acceleration equation.
USE YOUR NOTES, BOOK, and ELECTRONICS TO SOLVE!
CIRCUS FORCE DIAGRAMS
 What are 4 common forces?
 Draw force diagrams of a ball in juggler’s hand and in the air.
 Draw a force diagram for the wooden block