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Please prepare a piece of graph paper to plot a curve defined by several points. Interpret the grid lines such that you can plot values ranging from 0 to 10000feet on the vertical axis and you can plot values ranging from 0 to 30 seconds on the horizontal axis.
JavaScript code
Copy the code from Listing 3 into an html file and open it in your browser.
| Listing 3 . A plotting exercise. |
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<!-- File JavaScript03.html --<<html<<body<<script language="JavaScript1.3"<//Function to compute free-fall distance for a given time
// interval in seconds.function distance(time){
var g = -32.174; //acceleration of gravity in feet/sec^2var d = 0.5 * g * time * time;//(feet/sec^2)*sec^2 = feet
return new Number(d.toFixed(0));}//end function
//Compute the height of the rock every two seconds from// release until the rock hits the ground.
var t = 0;//secondswhile(t<= 30){
d = distance(t);//distance traveled in feeth = 10000 + d;//height in feet//Don't allow the height to go negative (underground)
if(h<0){
h = 0;}//end if//Display time and height at current time.
document.write("time = " + t +" height = " + h + "<br/<");
t = t + 2;}//end while
document.write("<br/>The End")</script<</body<</html< |
The screen output
When you open the html file in your browser, the text shown in Figure 7 should appear in your browser window.
| Figure 7 . Screen output for Listing #3. |
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time = 0 height = 10000
time = 2 height = 9936time = 4 height = 9743
time = 6 height = 9421time = 8 height = 8970
time = 10 height = 8391time = 12 height = 7683
time = 14 height = 6847time = 16 height = 5882
time = 18 height = 4788time = 20 height = 3565
time = 22 height = 2214time = 24 height = 734
time = 26 height = 0time = 28 height = 0
time = 30 height = 0The End |
Plot the data
Plot the 16 points shown in Figure 7 . Your horizontal axis should be the time axis and your vertical axis should be the height axis.
If we have both done everything correctly, the shape of your curve should be an upside-down parabola with its high point at a value of 10000. (If the wordparabola is new to you, don't worry about it. It's not important for the purpose of this module.)
The graph
Figure 8 shows an image of the graph that describes the trajectory of the falling rock. Asusual, please ignore the lower-case letters scattered throughout the image. They were placed there when the image was used for a different purpose earlier.
Figure 8 - The trajectory of the falling rock.
Change in height increases with time
Getting back to the height versus time values shown in Figure 7 and plotted in Figure 8 , the value for height should decrease for each successive time value.
Also, the change in height should increase for each successive time interval until the height goes to zero. The height goes to zero when the rock has landed on theground somewhere between 24 and 26 seconds. It continues at zero after that.
(Note that I put code into the script to prevent the value of height from going negative.)
The increase in the change in the height value during each successive time interval is the result of the time being squared in the equation given earlier . It is also the result of the acceleration of gravity that causes the downward speed of the rock to increaseas the rock falls.
Analysis of the code
Listing 3 calls a function copied from the previous exercise inside a while loop to compute the distance traveled and the resulting height for a series of time values ranging from 0 to 30 seconds intwo-second intervals.
Those values are displayed as shown in Figure 7 .
Understanding the code in Listing 2 and Listing 3 is important. However, it is more important at this point that you understand the handling of units asshown in the comments in the code.
I encourage you to run the scripts that I have presented in this lesson to confirm that you get the same results. Copy the code for each script into atext file with an extension of html. Then open that file in your browser. Experiment with the code, making changes, and observing the results of your changes. Makecertain that you can explain why your changes behave as they do.
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDFfile for this module at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should be aware thatsome of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.comshowing me as the author. I neither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, pleasebe aware that it is a copy of a module that is freely available on cnx.org and that it was made and published without my prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
-end-
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