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  1. #1
    johnWeldon is offline Member
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    Feb 2013
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    Default Assignment involving for and while loops

    So my prof just handed out this assignment. It's basically calculating the time it would take for an object at a certain height to hit the ground. Then comparing that to the analytical answer (formula)

    Here's what I have so far

    Java Code:
    package egr118;
    public class Lab3 {
        public static void main(String[] args) {
            double g = 9.807; //acceleration due to gravity
            double p_0 = 5; // initial height in meters
            double p = p_0; // p starts at p_0
            double v_0 = 0; // no velocity
            double dt = 1./10; // time step in seconds
            double t = 0; // start at time 0
            double at = 0;
            while (p>0)
                p = v_0 * t - 0.5 * g * t * t + p_0; //basically physics equation to determine position
                t += dt;
            System.out.println("Final Time = " + t);
            at = timeOfFlight(g , p_0); // analytical time using method below
            System.out.println("Analytical answer = " + at);
            double error = (((t - at) / at)* 100);
            System.out.println("\nThere is a " + error + "% error" );
        public static double timeOfFlight(double g, double p_0) // we have to create a new method to do the analytical answer for us
            return (double) Math.sqrt(2*p_0 / g);

    So the output would give us the time based on the formula above and the analytic formula in the new method. And then compare them and print out the error percentage.

    Now I'm on to the 3rd step which says:

    3) "Place the code so far inside of a "for" loop so that you can repeat your calculations faster. Change the double dt = 1./10 to double dt = 1./Math.pow( 2 , i );

    for ( int i = 1; i < 6; i++ )
    double dt = 1./Math.pow ( 2 , i );

    What do you think he means by place it in a for loop? I already have a while loop in the i keep it and leave it inside the for loop?

    Thanks for any help

  2. #2
    johnWeldon is offline Member
    Join Date
    Feb 2013
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    Default Re: Assignment involving for and while loops

    I just placed the while loop inside the for loop. It never states to replace it so I just left it.

    Now I have an extra credit portion

    I have to modify the code to output all of the values as they are computed, load them into a spreadsheet, and plot the height vs time.

    I have NO idea how to do that...i get the outputs as they are received I can just place the

    Java Code:
    inside the loop.

    But how do I load them into a spreadsheet or anything like that?

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