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Screen output
When you open the html file in your browser, the text shown in Figure 6 should appear in your browser window.
| Figure 6 . Screen output for Listing #2. |
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At 10 seconds:
distance traveled = -1609 feetheight = 8391 feet
At 20 seconds:distance traveled = -6435 feet
height = 3565 feetThe End |
As you can see from Figure 6 , after ten seconds, the rock will have traveled a distance of -1609 feet. (The minus sign indicates downwardmotion.)
Adding this value to the initial height of 10000 feet produces a value of 8391 for the height of the rock at the end of 10 seconds.
Similarly, Figure 6 gives us 3565 for the height of the rock at 20 seconds.
Analysis of the code
The code in Listing 2 begins by defining a function that computes and returns the distance traveled for a rock falling toward the earth for a given timeinterval since release assuming that the initial velocity was zero (the rock was simply dropped).
This function implements the equation shown earlier, and expects to receive the time as an input parameter. It returns thedistance traveled during that time interval.
Note that the interaction of units is shown in the comments with the result that the returned value is in feet.
Call the function twice in succession
Then the code calls that function twice in succession for two different timeintervals (10 seconds and 20 seconds) to determine the distance traveled during each time interval.
In both cases, the distance traveled is added to the initial height of 10000 feet to determine the height of the rock at the end of the time interval.
Also, in both cases, the time interval, the distance traveled, and the resulting height of the rock above the ground are displayed as shown in Figure 6 .
Note again that in all cases, the interactions of the various units are shown in the comments.
Let's do another exercise and this time plot the results.
Please prepare your plot board 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.
A tactile graph
If you have an assistant who will download the zip file named Phy1050.zip , extract the file named Phy1050a1.svg, and use that file to create a tactilegraph as described in the module named Manual Creation of Tactile Graphics . You can explore the tactile graph instead. Regardless, you should write the script and examine the printed output as described in thefollowing paragraphs.
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< |
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