Stella Model: Acceleration
| Table of Contents | |
| Page No. | Topic |
| Page 3 |
Kinematics and Dynamics: Overview, Skills Required, & EALRs |
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Page 4 |
Stella Model: Constant Velocity |
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Page 8 |
Stella Model: Acceleration Stella Model: Free FallPage |
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Page 12 |
Stella Model: Newton’s Laws of MotionPage |
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Page 16 |
AppendixPage |
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Page 20 |
Stella Model: Constant Velocity AnswersPage |
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Page 21 |
Stella Model: Acceleration AnswersPage |
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Page 23 |
Stella Model: Free Fall AnswersPage |
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Page 26 |
Stella Model: Newton’s Laws of MotionPage |
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Page 30 |
Assessment for Stella Modeling of Kinematics & DynamicsPage |
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Page 35 |
Assessment AnswersPage |
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Page 37 |
Scoring Rubric for AssessmentsPage |
| Page 39 | Links to Sites for STELLA Modeling |
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Part I.
Open the file Constant Acceleration Model.The model should look like this:
Double-click on the Rate of Change of Distance icon, and when the window opens, Velocity should have been selected from the Required Inputs box. Click OK.Double-click on the Velocity stock and type the number 0 and OK.Double-click on the Rate of Change of Velocity icon and Acceleration should have been selected from the Required Inputs box. Click OK. The circular icon, Acceleration, is known as a converter Double-click on the Acceleration converter and the number 3 should be typed in the Required Inputs box.1. In the Constant Velocity STELLA Model, the Rate of Change of Distance was equal to a constant (7). Why can we now equate Rate of Change of Distance with Velocity?
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Double-click on the Graph 1 icon.>Distance, Velocity, and Acceleration have beenselected and the scales have been set. Run the model.
2. a. Sketch the graph and identify which line is Distance, Velocity, and Acceleration.
b.Describe the appearance of the lines for Distance, Velocity, and Acceleration.
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3.In the Velocity stock, change the initial velocity to 5. Run the model anddouble-click on Graph 1. Describe the appearance of the graph and explain what ishappening to Distance and Velocity.
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4.In the Velocity stock, change the initial velocity to 0 and change the Accelerationconverter value to
5.Run the model and double-click on Graph
1.Describe theappearance of each graph and explain what is happening to Distance, Velocity, andAcceleration.
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Part II: Extensions
Experiment with changing the acceleration values (Acceleration converter), initial velocity (Velocity stock) and the initial distance (Distance stock). Remember to use appropriate testing procedures: change one variable at a time.For the moment, keep all values positive.
5.What were the effects on the graphs when you changed each of these variables?
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6.Predict the effect of having a negative acceleration. What will all the graphs look likeif the initial distance and velocity start at zero? Sketch your answer on the graphbelow.
To check your prediction, make the following changes in the model.Double-click on the Distance stock and in the upper left corner of the dialog box, click in the Non-negative box so that it is blank (no X).Click OK.Repeat this for the Velocity stock.This allows both of these variables to go negative.Now double-click on the Rate of Change of Distance flow and in the upper left corner of that dialog box, click in the BIFLOW bullet.Click OK.Repeat for the Rate of Change of Velocity flow.This allows the flows to add or subtract amounts from the stock.Now change the value in the Acceleration converter to a negative number (try -3).
Click on Graph 2 and the dialogue box should open. In the Selected box, highlight Distance and in the Scale box change Min to -250 and Max to 50 and click on Set.Highlight Velocity and set Min to -40 and Max to 0.Finally, highlight Acceleration and set Min to -4 and Max to -2.
Run the model.Click on Graph 2 and observe.
7.Sketch and explain the appearance of the graph.
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STELLA can be used to model a car accelerating, traveling at constant velocity and then decelerating.Double-click on the Acceleration converter.Type the following in place of the negative value you just used above:
If (Time < 3) then 5 else if (time > 9) then -5 else 0
This statement says, that if time is less than 3 seconds, the car will accelerate at 5, it will stop accelerating at all between 3 and 9 seconds and then at 9 seconds, it will decelerate at the rate of -5.Run the model.Click on Graph 3 and observe the results. 8.Describe the graph created by the model.
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