Transcript Motion Unit 3 2016x

Unit 4:
Motion
Name:
Period:
89
Motion
Definition: change in position relative to a reference point or frame of
reference.
How do we know something is moving (in motion)?
Frame of reference: place or object used for comparison to tell if an
object is in motion.
What is a frame of reference to tell that the marker is moving from one place
to another when writing on the white board?
Examples of motion that are easy to detect:
_________________________
_________________________
_________________________
_________________________
These types of motion have an obvious
Examples of motion that are not easy to detect:
_________________________
_________________________
_________________________
_________________________
These types of motion don’t have an obvious
In the box, draw a picture of
something in motion and the
frame of reference that is used
to determine motion:
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Kinetic and Potential Energy
Kinetic and potential energy have a lot to do with the motion of objects –
for example a roller coaster.
When the roller coaster is at the top of a hill, it has a lot of POTENTIAL
ENERGY because it is high off the ground.
When the roller coaster is at the bottom of a hill, it has a lot of KINETIC
ENERGY because it is moving very fast.
Kinetic energy = energy of
Potential energy =
Type of Energy
energy
Factors amount of energy depends
on
Factor 1
Kinetic
mass
(Gravitational)
Potential
mass
Formula
Factor 2
P.E. = mgh
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Law of Conservation of Energy:
energy cannot be created or destroyed, it can
only change form.
When an object moves down a ramp, its
increases and its
energy
energy decreases.
When you add the kinetic and potential energy together at one of
the spots, what is the total amount of energy (in Joules)? _______
As the person’s position changes, the amount of potential energy
and kinetic energy goes up and down, but the total amount of
energy stays the
(as long is there is no air
resistance and no friction).
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Calculating Speed, Time or Distance of an Object
Speed: the distance traveled by a moving object per unit of time.
To calculate speed, distance or time – use the formulas below:
Sample Problems:
A girl travels 20 miles on her bicycle. The trip takes 2 hours. Express her
speed in miles/hr.
distance (d) = 20 miles
S = d/t
time (t) = 2 hours
S = 10 mi/hr
1. What is the speed of a rocket that travels 9000 meters in 12.12 seconds?
2. How far (in meters) will you run in 40 seconds running at a rate of 5 m/s?
3. How long will your trip take (in hours) if you travel 350 km at an average
speed of 80 km/hr?
4. A trip to Cape Canaveral, Florida takes 10 hours. The distance is 816 km.
Calculate the average speed.
5. The space shuttle makes one orbit around earth (25,840 miles) in 1.5
hours. What is its average speed.?
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Types of Speed:
Average speed:
If it takes you 10 seconds to run 25 meters, your average speed is 2. 5 meters per
second (2.5 m/s). To calculate average speed, you simply take the total distance
traveled divided by the total time taken.
Average speed =
distance /
time
Average speed for 0- 4 sec.:
Total distance:
Distance
(meters)
Total Time:
Speed:
Average speed for 0- 8 sec.:
Total Distance:
18 meters
Total Time:
Time (seconds)
Speed:
Instantaneous Speed:
At some points along the way, you may go slower or faster than average. The
instantaneous speed is the speed you have at a specific point in your journey.
You might go uphill at 1 m/s and downhill at 3 m/s, with an average speed of 2.5 km/h
even though your speed may have been 2.5 km/h only momentarily during the trip!
A speedometer shows
speed.
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Investigation: Measuring Time
How is time measured accurately?
A measurement is a quantity with a unit that tells what the quantity
means. For example, 3 seconds is a measurement of time that
includes a quantity (3) and a unit (seconds). This investigation will
explore time measurement.
Using the photogates
A photogate allows us to use a light beam to start and stop the timer. When the
timer is in interval mode, it uses photogates to control the clock.
1. Connect a single photogate to the
“A” input with a cord.
2. Select interval on the timer.
3. Push the “A” button and the “A”
light should come on and stay on.
4. Try blocking the light beam with your finger and observe. Use your observations
to fill in the first row of the data table at the bottom of the page.
5. Connect a second photogate to the socket behind the B button (input B). You
should now have two photogates connected to the timer. Make sure the light on
each photogate is green and press the reset button.
6. Pressing reset clears the clocks and also tells the timer to look at its inputs to see
which photogates are connected.
7. Experiment to find out what starts and stops the displayed time for each
combination of the A and B lights . Fill in the table with your observations
A
light
B
light
on
off
off
on
on
on
How do you start the
clock?
How do you stop the clock?
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CPO Exploration: Calculating Speed
Speed describes how fast or slow something moves. You have to put two quantities
together to describe your speed: the distance you traveled, and the time it took you to
go that distance. An average walking speed is 1 m/s, or 100 cm/s. What is the
average speed of the car as it rolls down the ramp?
A. Set up your car and ramp
1. Set up the car and ramp as instructed by your teacher. Each group will put the
ramp in a different hole of the physics stand. This means each group will have a
different ramp angle. All groups will calculate the speed of the car.
2. Identify the independent and dependent variables for this experiment:
Independent variable:
Dependent variable:
3. Describe how three variables will be controlled in this experiment:
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
B. Your hypothesis
a. Look around at the other groups and compare the ramp angles.
b. Write your hypothesis, stating which ramp will have the fastest car. Explain the
reasoning behind your hypothesis.
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C. Find the average speed of the car
1. Record the distance between the two photogates.
2. Roll the car down the ramp and record the time it
takes to go from photogate A to B. Be sure to read
the timer when the A and B lights are both on!
3. Find the average speed by dividing the
distance by time (speed = distance/time).
4. Do two more trials so you have a total of
three trials. Find the average speed from
your three trials. All speed measurements should be to the nearest whole number.
Analyzing your results
a. Create a class data table that shows the average speed for each different ramp
position.
# of holes
Average Speed
# of holes
Average Speed
b. Do the groups’ speeds agree with your hypothesis about which ramp should have the
fastest car? Why or why not?
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D. Find the instantaneous speed of the car
To find the instantaneous speed of the car, you need to know two things: the distance
traveled through the photogate, and the time it takes the car to go that distance.
With one photogate, the timers measure the time that the beam is broken. As the car
passes through the photogate, the light beam is broken for the width of the wing.
The speed of the car is the width of the wing (distance traveled) divided by the time it
takes to pass through the light beam (time taken). The advantage to this technique is that
it is easy to move a single photogate up and down the ramp to make measurements of
the speed at many places.
1. Pick five locations along the track, and record those locations in the first column.
2. Put photogate A at each location (make sure only A is turned on), release the car from
the top of the ramp, and record the time it takes the car to pass through photogate A.
3. Use the information above to calculate the speed at each location to the nearest whole
number
Table: Position vs. Speed
Position of
photogate B
(cm)
Distance car
traveled as it went
through photogate A
(cm)
Time
through
photogate A
(sec.)
Speed of car at
photogate A
(cm/s)
5
5
5
5
5
4. Use the information in your data table to construct a graph of positon vs. speed using
the grid on the next page.
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5. Analysis Questions:
1. What happens to the speed of the car as it goes down the ramp?
2. What happens to the car’s kinetic and potential energy as it travels
down the ramp?
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Using a Graph to Calculate Speed
C.
B.
A.
Use the graph to calculate:
1. The car’s speed for the first one hour (segment A):
Speed = rise (change in y) =
run (change in x)
=
m/hr
2. The car’s speed between 1 and 1.5 hours (segment B):
Speed = rise =
run
=
m/hr
2. The car’s speed for the last 0.5 hours (segment C):
Speed = rise =
run
=
m/hr
3. The car’s average speed for the entire 2 hours:
Average speed = total rise =
total run
m/hr
4. During which segment did the car have the most kinetic energy?
5. During which segment did the car have the least kinetic energy?
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Graphing Motion: Reading a Graph
Decide what each graph “says” about the speed of the object.
1.
*speed at 2s? ______
*speed at 4s? ______
This graph shows
speed.
2.
*speed at 2s? ______
*speed at 4s? ______
This graph shows
3.
This graph shows that runner A
is
than
runner B.
speed.
4.
This graph shows that Sam
on
his way to school.
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Speed vs. Velocity
MTA
Speed only gives
not direction.
and
Velocity gives an object’s speed AND its
,
.
Velocity: speed in a given direction.
Velocity gives distance, time, and the direction of travel.
What’s the plane’s velocity?
What is the train’s speed?
Examples of jobs where knowing velocity would be more important than
just knowing speed:
________________________________________________
________________________________________________
_________________________________________________
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Tracking a Hurricane
Hurricane Andrew (August 1992) was one of the most devastating storms of
the twentieth century. Originally labelled a Category 4 storm, it was recently
upgraded to a Category 5, the most severe type of hurricane. Scientists use
satellite data and weather instruments dropped by aircraft to measure the
storm’s intensity. As research techniques improve, weather experts can more
accurately analyze data collected by these instruments. NOAA scientists
have now determined that Andrew’s sustained winds reached at least 165
miles per hour. In this activity, you will track Hurricane Andrew’s treacherous
journey.
The storm’s beginning
Hurricane Andrew was born as a result of a tropical wave which moved off
the west coast of Africa and passed south of the Cape Verde Islands. On
August 17, 1992, it became a tropical storm. That means it had sustained
winds of 39-73 miles per hour.
1. At 1200 Greenwich Mean Time (GMT) on August 17, Tropical Storm
Andrew was located at 12.3°N latitude and 42.0°W longitude. The wind
speed was 40 miles per hour. Plot the storm’s location on your map.
2. For the next four days, Tropical Storm Andrew moved uneventfully westnorthwest across the Atlantic. Plot the storm’s path as it traveled toward
the Caribbean Islands.
Date
Time
(GMT)
Latitude
(0N)
Longitude
(0W)
Wind Speed
(mph)
8/18/92
1200
14.6
49.9
52
8/19/92
1200
18.0
56.9
52
8/20/92
1200
21.7
60.7
46
8/21/92
1200
24.4
64.2
58
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The storm intensifies
Late on August 21, a deep high pressure center developed over the southeastern
United States and extended eastward to an area just north of Tropical Storm Andrew.
In response to this more favorable environment, the storm strengthened rapidly and
turned westward. At 1200 GMT on August 22, the storm reached hurricane status,
meaning it had sustained winds of at least 74 miles per hour.
1. Plot Hurricane Andrew’s path over the next two days.
Date
Time
(GMT)
Latitude
(0N)
Longitude
(0W)
Wind Speed
(mph)
8/22/92
1200
25.8
68.3
81
8/23/92
1200
25.4
74.2
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2. Hurricane watches are issued when hurricane conditions are possible in the area,
usually within 36 hours. Hurricane warnings are issued when hurricane conditions are
expected in the area within 24 hours. Look at the distance the hurricane travelled in
the last 24 hours and use that information to predict where it might be in 24 hours, and
in 36 hours. Name one area that you would declare under a hurricane watch, and an
area that you would declare under a hurricane warning.
Hurricane watch(area affected within 36 hours:
Hurricane warning(area affected within 24 hours)
Landfall
On the evening of August 23, Hurricane Andrew first made landfall. Landfall is defined
as when the center of the hurricane’s eye is over land.
1. Plot the point of Hurricane Andrew’s first landfall.
Date
Time
(GMT)
Latitude
(0N)
Longitude
(0W)
Wind Speed
(mph)
8/23/92
2100
25.4
76.6
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2. Where did this first landfall occur? Include the country and the coordinates.
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Hurricane Andrew crosses the Gulf Stream and strikes the U.S.
During the night of August 23, Hurricane Andrew briefly weakened as it moved
over land. However, once the storm moved back over open waters, it rapidly
regained strength. The warm water of the Gulf Stream increased the intensity of
the hurricane’s convection cycle. At 0905 GMT on August 24, Hurricane Andrew
made landfall again.
1. Plot the point of Hurricane Andrew’s next landfall.
Date
Time
(GMT)
Latitude
(0N)
Longitude
(0W)
Wind Speed
(mph)
8/24/92
0905
25.5
80.3
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2. Where did this first landfall occur? Include city, state and coordinates.
The final landfall
After making its first landfall in the United States (where it caused an estimated
$25 billion in damage), Hurricane Andrew moved northwest across the Gulf of
Mexico. On the morning of August 26, 1992, Hurricane Andrew made its final
landfall. Afterward, Andrew weakened rapidly to tropical storm strength in about
10 hours, and then began to dissipate.
1. Plot Andrew’s course across the Gulf of Mexico and its final landfall.
Date
Time
Latitude
Longitude
Wind Speed
(GMT)
(0N)
(0W)
(mph)
8/24/92
1800
25.8
83.1
133
8/25/92
1800
27.8
89.6
138
8/26/92
0830
29.6
91.5
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2. In which state did Hurricane Andrew’s final landfall occur?
Follow-Up Question:
Why is it important to know the velocity (not just the speed) of a hurricane?
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18
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CPO Exploration: Acceleration
What kind of motion happens when an object rolls down a hill?
Scientists and engineers use two graphs to quickly describe motion. One is the graph
of position versus time. The other is the graph of speed versus time. In this
investigation you will make a speed versus time graph for the car.
1. How to find the speed of the car at different points along the ramp
Using two photogates far apart gives you a measure of the average speed of the car
between the photogates. The car could be going faster at the lower photogate and
slower at the upper one. To get a true picture of how the speed of the car changes,
you will need to measure the speed with one photogate.
Remember, with one photogate the timers measure the time that the beam is broken.
As the car passes through the photogate, the light beam is broken for the width of the
wing. The speed of the car is the width of the wing (distance traveled) divided by the
time it takes to pass through the light beam (time taken). The advantage to this
technique is that it is easy to move a single photogate up and down the ramp to make
measurements of the speed at many places.
2. Measuring position versus time
A. Set up the ramp and physics stand with the
ramp through the 6th hole up on the stand.
B. Put photogate A at the 10 cm position.
C. Move photogate B to 6 different positions
10 cm apart along the track starting at 20 cm.
D. For every position of photogate B,
record the time through the beam at
Photogate B and also the time from A to B.
E. Take 6 data points along the ramp
being careful to start the car the same way every time.
Record all your data in the table on the next page.
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3. Find the car’s speed
Use the information in your data table below, and the information on the first page to
calculate the speed of the car at each of the six points.
For each position of Photogate B, divide the distance (5) by the time through
Photogate B.
Round the speed to the nearest whole number.
Table 3-3: Time A-B vs. Speed of the car at photogate B
Position of
photogate
B
(cm)
Time from
photogate
A to B
(sec.)
Distance car
traveled as it went
through photogate
B
(cm)
20
5
30
5
40
5
50
5
60
5
70
5
Time
through
photogate
B
(sec.)
Speed of car
at
photogate B
(cm/s)
4. The speed versus time graph
a. The y-axis of this graph is going
to be the speed of the car
at photogate B.
b. The x-axis of your graph is
the time from A to B.
c. Plot the speed at B versus
the time from A to B.
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5. Analysis Questions:
1. What shape does the speed versus time graph have?
2. What happens to the car’s speed as it goes further down the ramp?
3. Where does the car have the most kinetic energy?
4. Where does the car have the most potential energy?
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Acceleration
Acceleration:
any change in the speed and/or direction of an object.
=
Increasing speed
(positive accel.)
= Changing direction
= Decreasing speed
(negative accel.)
Acceleration on a roller coaster:
Label one place on the roller coaster that has positive acceleration (S+), one
place that has negative acceleration (S-) and one place where the car is
accelerating from a change in direction (CinD).
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CPO Exploration: Energy Transformations on a Roller Coaster
Where does the marble move the fastest, and why?
To pedal your bicycle up a hill, you have to work hard to keep the bicycle moving.
However, when you start down the other side of the hill, you can coast! In this
investigation, you will see how a marble’s speed changes as it moves up and down
hills. It’s all about energy!
1. Set up the roller coaster
A. Attach the roller coaster to
the fifth hole from the
bottom of the stand.
B. Place the marble against the
starting peg and let it roll
down the track.
C. Watch the marble roll along
the track. Where do you
think it moves the fastest?
2. Hypothesis
a. Think about the seven places in the diagram below:
A. Where do you think the marble is moving the fastest? Choose
one of the seven places and write down why you think that will be the
fastest place?
B. Where do you think the marble is moving the slowest? Choose
one of the seven places and write down why you think that will be the
slowest place.
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3. Testing your idea
A. Set the timer in interval mode and plug a
photogate into input “A.”
B. Put the photogate at the first position. Use a
meter stick to measure the height of the photogate
off the ground.
C. Measure the time it takes the marble to roll
through the photogate at each of the seven
places. Be sure the photogate is pushed up
against the bottom of the track.
D. The speed of the marble is its diameter divided by the time it takes to pass through
the photogate. Find the speed of the marble at each position by dividing the diameter
of the marble (1.9 cm) by the time through photogate A.
E. Repeat for other six positons.
Table 3-4: Speed of the Marble
Position
#
Position
(cm)
Height Off
Ground (cm)
Distanc
e (cm)
1
5
1.9
2
25
1.9
3
45
1.9
4
65
1.9
5
85
1.9
6
105
1.9
7
125
1.9
Time A(s)
Speed (cm/s)
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6. Graphing Data:
a. Make a graph with the height on
the y-axis and the position on the x-axis.
b. Scale the right hand side so you
can plot speed on the same graph.
Use the example in the
diagram.
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4. Analysis Questions
a. Which position was fastest? Did the data support your hypothesis?
b. The marble has more potential energy at the top of the roller coaster than at the
bottom. What happens to the potential energy as the marble rolls down the ramp?
c. Energy can’t be created or destroyed so the marble potential energy at the top of the
track had to come from somewhere or someone. What or who transferred energy to the
marble?
5. Calculating Potential and Kinetic Energy.
a. Fill in the table below to calculate the potential energy of the marble at the beginning
and end of the track. PE = mass x gravity x height
Mass of marble X Force of Gravity X
5 g
9.8 m/s2
5 g
9.8 m/s2
Height (cm)
Energy (mJ)
=
b. Fill I the table below to calculate the kinetic energy of the marble at the beginning and
end of the track. The formula for kinetic energy is
Mass of
marble
X
Speed of the marble2
(cm/s)
Divided by
5 g
2
5 g
2
=
Energy (mJ)
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6. Conclusion:
a.
b.
The marble is going fastest when it is at the
height
The marble is going slowest when it is at the
height.
The Law of Conservation of Energy states that the total amount of
energy in a system stays the same (if there’s no friction).
c.
d.
As the marble goes downhill, its
energy increases and its
decreases.
As the marble goes uphill, its
increases and its
energy
energy
energy decreases.
3. Use the letters a-f on the roller coaster outline to show where each
item is occurring.
a.
Maximum kinetic energy (MKE)
b.
Maximum potential energy (MPE)
c.
Kinetic energy increasing (KE
d.
Kinetic energy decreasing (KE
)
e.
Potential energy increasing (PE
)
f.
Potential energy decreasing (PE
)
)
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Momentum
Momentum: the product of the mass of an object and its velocity (speed).
All moving objects have momentum.
To calculate momentum, use the equation:
Momentum = Mass x Velocity
Calculate momentum for the two vehicles at 100 km/hr:
Car
Mass (kg)
Speed (km/hr)
Momentum
(kg●km/hr)
1240
Porsche Boxster
2979
Hummer
Conservation of Momentum: When objects collide, momentum is
transferred from one object to another - the total momentum stays the same.
Fill out the table below based on your observations of how many marbles move off
the end of the ramp when different amounts of marbles are sent down the ramp.
# of marbles released from top # of marbles pushed off of
of ramp
bottom of ramp
1
2
3
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Momentum Lab
Part I: Calculating Momentum
Procedure:
a. Set up the pipe wrap insulation ramp on 2, 3 and 4 books. Be sure to tape the ends
down
b. Record the time it takes the marble to roll down the ramp. The ramp is 90 cm long.
c. Calculate the (speed) velocity of the marble using the formula:
v = d/t
d. Using a triple beam balance, find the mass of the marble.
e. Using the formula below, calculate the momentum of the marble at each height.
Momentum (p) = mass • velocity*
Note: in this case, velocity and speed are the same thing.
Data and Observations:
Table 3 – 7: Momentum of Marble
Height of Ramp Mass of Marble
(# of books)
(grams)
Time
(s)
Marble’s Speed
(cm/s)
2
90 =
time
3
90 =
time
4
90 =
time
Momentum
(g•cm/s)
Analysis Questions:
a. On which ramp does the marble have the most momentum? Which factor (mass or
speed) increased when momentum increased?.
b. What is the relationship between speed and momentum?
As speed increases, momentum
.
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Part II: Transfer of Momentum from the Marble to a Cup
Procedure:
a. Set the ramp up on 2, 3, and 4 books. Measure the height for each ramp in
centimeters and record.
b. Place the cup at the end of the ramp so that the opening faces the end of the
ramp.
c. Tape a ruler to the table so that 0 cm on the ruler is even with the front of the cup.
c. Release the marble from the top of the ramp and observe how far the cup moves
when hit by the marble. Repeat once at each height and record data below.
d. Calculate the average distance the cup moves.
Data and Observations:
Table 3– 8: Height of Ramp vs. Distance Cup Moves
Height of Ramp
(cm)
Distance Cup Moves (cm)
Trial 1
Trial 2
Average
Analysis Questions:
a. Identify the independent and dependent variables in this investigation:
Independent variable:
Dependent variable:
b. What evidence does this investigation provide to support the Law of Conservation
of Momentum = the transfer of momentum from one object to another?
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c. Using the information in table 3 -8, create a line graph comparing the height of the
ramp to the distance the cup moves. The height of the ramp should be graphed on
the x axis and the distance the cup moves on the y axis. Remember title and labels.
Conclusion:
a. Complete the statement below to describe the relationship between the amount
of momentum the marble has and how far the cup moves.
As the amount of momentum
the cup moves
, the distance
.
b. On the diagram of the track below, label the point where the marble had the most
potential energy (MPE) and the point where the marble had the most kinetic
energy (MKE).
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Applications of Speed and Motion
Question: Why do you see lightning before
you hear thunder?
speed of sound at sea level = 340.29 m / s
Picture of an object that can travel
faster than the speed of sound (reality)
the speed of light = 299, 792, 458 m / s
Picture of object that can travel faster
than the speed of light (science fiction)
Answer:
Question: How is motion used to determine the units of time?
• Earth’s orbit around the sun
takes
.
•Average Speed = 30 km/s
• Earth rotating once on its axis
takes
.
•Average Speed = 465 m/s
•One cycle of moon phases takes
about one
Question: How does motion change the earth?
• Earth’s tectonic
are always moving , causing earthquakes .
Average Speed = 5 cm/yr
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Terms:
1. motion:
2. frame of reference:
3. kinetic energy:
4. potential energy:
5. Law of Conservation of Energy:
3. speed:
4. velocity:
5. acceleration:
9. momentum :
10. Conservation of Momentum :
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Term Review
Instructions: In the space below or on the lines below,
show that you understand the meaning of 6 of the 10 terms
for this unit. You can do this by writing a story, drawing a
picture(s) with captions, or a bit of both. Just be sure the
terms are underlined and your picture/story shows how the
term is used in context, not just as a definition.
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