Acceleration
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Acceleration
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Acceleration
Introduction
Journals and Snapshots
The Snapshot button is used to capture the
screen.
The Journal is where snapshots are stored
and viewed.
The Share button is used to export
or print your journal to turn in your
work.
Each page of this lab that
contains the symbol
should be inserted into your
journal. After completing a
lab page with the snapshot
symbol, tap
(in the upper
right corner) to insert the
page into your journal.
Note: You may want to take a
snapshot of the first page of
this lab as a cover page for
your journal.
Acceleration
Lab Challenge
• What does it mean to decelerate?
• What does it mean to accelerate?
Acceleration
Background
• Acceleration is the rate at which the velocity
of an object changes.
velocity final – velocity initial
time
= acceleration
• Since velocity is the speed and direction of
an object's motion, acceleration can mean
speeding up, slowing down, or changing
direction.
Acceleration
...Background
• A car can have a positive acceleration when it is
speeding up and a negative acceleration when it is
slowing down depending on its direction of travel.
• When a car is speeding up, its acceleration is in the
same direction of its velocity: both acceleration
and velocity are positive or negative. When a car is
slowing down its acceleration is in the opposite
direction of its velocity: velocity and acceleration
have opposite signs.
Acceleration
...Background
• Constant acceleration means that
an object's velocity is changing at
an uniform rate.
• For example, when you throw a ball
into the air it experiences a velocity
change of 9.8 m/s every 1 second.
Since the acceleration's direction is
pointing towards the Earth, the ball
will decelerate (slow down) when
moving up and accelerate (speed
up) when falling down.
Acceleration
Self-Check
1. When a car's acceleration is negative but its
velocity is positive, the car is:
a) slowing down
b) speeding up
c) maintaining constant speed
d) undefinable
Acceleration
Self-Check
2. Does a cart rolling freely up and then back down an inclined track
illustrate constant acceleration? Justify your answer.
Acceleration
Materials and Equipment
Collect all of these materials before
beginning the lab.
• Motion Sensor
• Cart with Plunger
• Track End Stop
• Track Pivot Clamp
• Dynamics Track
• Rod and Base
Note: Angle indicator not used
in this lab
Acceleration
Sequencing Challenge
A. Repeat data
collection, this time
pushing the cart up
the inclined track
toward the motion
sensor.
B. Determine the
cart's acceleration
from each trial
using the slope of
the graphed data.
C. Release the cart
from the elevated
end of the track to
produce a velocity
versus time graph.
D. Assemble the
inclined track with
the end stop at one
end and the motion
sensor at the
opposite end.
The steps to the left are part
of the procedure for this lab
activity. They are not in the
right order. Determine the
correct sequence of the
steps, then take a snapshot
of this page.
Acceleration
Setup
1. Attach the End Stop to the lower end of the
Dynamics Track.
2. Mount the track to your rod and base using the
pivot clamp, slightly inclining the track at one end.
3. Attach the Motion Sensor to the elevated end of
the track with the face of the sensor pointed down
the length of the track.
4. Connect the Motion Sensor to the SPARK Science
Learning System.
Note: Make certain the switch on the top of the motion
sensor is set to the cart icon.
Acceleration
Collect Data
1. Set the cart at the top of
the inclined end of the
track holding it ~15 cm
from the Motion Sensor.
2. Tap
to begin data
collection.
3. Release the cart allowing
it to roll down the track.
4. Catch the cart at the
bottom of the inclined
track just before it hits the
end stop.
5. Tap
to stop data
collection.
Acceleration
Collect Data
6. Set the cart at the bottom
of the inclined track against
the end stop.
7. Tap
to begin data
collection
8. Using your hand, push the
cart up the inclined track
(avoid hitting the motion
sensor) allowing it to roll
back down.
9. Again, catch the cart just
before it hits the end stop.
10.Tap
to stop data
collection.
Acceleration
Analysis
1. During the period when the cart was in motion, are the velocity versus time
graphs straight lines? Refer to the previous page if necessary. How is the
acceleration of the cart changing if your velocity versus time graphs are straight
lines?
Acceleration
Analysis
2. Although the paths of the cart in both trials were different, the slopes of the
velocity versus time graphs for each trial are the same (during the period in which
the cart was in motion). Why is this the case? Justify your answer.
Acceleration
Analysis
3. Looking at the velocity
versus time graph, what
would a negative slope tell
you about the cart's
acceleration? A positive
slope?
Acceleration
Analysis
4. What was causing the cart
to accelerate after
releasing it from rest at the
top of the track? Was that
acceleration constant?
Acceleration
Analysis
5. Describe the motion of an object whose velocity versus time graph is a horizontal
straight line (a slope of zero).
Acceleration
Synthesis
1. The term "acceleration" is used in our everyday lives and language, but is often
used in a non-physical context. Now that you have developed a physical definition
of "acceleration" give an example where the physical definition matches the
"everyday" definition. Give an example where
they are different.
Acceleration
Synthesis
2. Modern aircraft carriers use a steam powered
catapult system to launch jets from a very short
range. These catapults can provide a constant
acceleration to bring jets up to speed in only 2
seconds. If each jet requires a minimum takeoff speed of 82.3 m/s, how much acceleration
must the catapult supply so the jet can take off?
Acceleration
Synthesis
3. How many different devices in a car help to accelerate the vehicle?
What are they?
Acceleration
Multiple Choice Question
1. If the acceleration due to gravity is -9.8 m/s2, which
of the following choices would best describe the
acceleration of a 0.5 kg frictionless block sliding
down the track used in our experiment?
a) -3.5 m/s2
b) 3.5 m/s2
c) 0 m/s2
d) Undefinable
Acceleration
Multiple Choice Question
2. A cart with an initial velocity of zero and a final
velocity of 12 m/s after 2 s will have an
acceleration of
a) 4 m/s2
b) 6 m/s2
c) 8 m/s2
d) 12 m/s2
Acceleration
Multiple Choice Question
3. A race car starting from rest accelerates uniformly
at a rate of 5 m/s2. What is the car's speed after it
has traveled for 5 s?
a) 5 m/s
b) 10 m/s
c) 20 m/s
d) 25 m/s
Acceleration
Congratulations!
You have completed the lab.
Please remember to follow your teacher's instructions for cleaning-up and submitting
your lab.
Acceleration
References
ALL IMAGES WERE TAKEN FROM PASCO DOCUMENTATION, PUBLIC DOMAIN CLIP ART, OR WIKIMEDIA
FOUNDATION COMMONS:
http://commons.wikimedia.org/wiki/File:070825-N-3271W-004.jpg
http://commons.wikimedia.org/wiki/File:StappSled.jpg
http://commons.wikimedia.org/wiki/File:Rocket_sled_track.jpg
http://commons.wikimedia.org/wiki/File:F-14D_Tomcat_on_USS_John_C._Stennis.jpg
http://commons.wikimedia.org/wiki/File:FA-18-Decollage.jpg
http://commons.wikimedia.org/wiki/File:Paul_Menard,_Homestead-Miami_2006.jpg
http://upload.wikimedia.org/wikipedia/commons/1/14/F-15_takeoff.jpg
http://commons.wikimedia.org/wiki/File:Ford_BA_Falcon_GT_-_Targa_Tasmania.jpg
http://www.freeclipartnow.com/office/paper-shredder.jpg.html