If you fire a projectile fast enough, the curve of the earth will match the spee

Question

If you fire a projectile fast enough, the curve of the earth will match the speed at which the projective falls. The projectile will then orbit the earth. The speed, in meters/second necessary to orbit the earth at an altitude h can be calculated by velocity = Squareroot G Me /R + h where: G is the universal gravitation constant, 6.67408 times 10^-11 (written 6.67408e-1 1 in Java) Me is the mass of the earth, 5972 times 10^24 Kg R is the radius of the earth, 6.371 times 10^6 meters h is the height of the orbiting object in meters Write a program that asks the user the altitude of an obit in kilometers and then displays the velocity in meters/second. Note that there are 1000 meters in a kilometer. You will have to convert the input from kilometers to meters. Sample input and output Enter the orbit altitude in Km 225 The orbit speed is 7773.476322849655 m/s Most people in America are more familiar with miles than meters. Modify your program to input the altitude in miles and display the result in miles/hour. There are 1.60934 kilometers in a mile and 2.23694 miles/hour in one meter/second. Convert the input from miles to km and the result of the calculation from m/s to mph.

Explanation / Answer

Solution of 2A :

import java.util.Scanner;   //to use Scanner class
import java.lang.Math;       //to use Math class which contains sqrt() and pow() functions
class Velocity
{
   public static void main(String args[])
   {
       Scanner obj=new Scanner(System.in);
       double G=6.67408e-11;
       double Me=5.972*Math.pow(10,24);       //using pow() of Math class
       double R=6.371*Math.pow(10,6);           //using pow() of Math class
       double h,velocity;
       System.out.println("Enter the orbit altitude in Km");
       h=obj.nextDouble();                        //using nextDouble() of Scanner class
       h=1000*h;
       velocity=Math.sqrt((G*Me)/(R+h));         //using sqrt() of Math class
       System.out.println("The orbit speed is "+velocity+" m/s");
   }
}

Solution of 2A :

import java.util.Scanner;    //to use Scanner class
import java.lang.Math;        //to use Math class which contains sqrt() and pow() functions
class VelocityInMilesPerHour
{
    public static void main(String args[])
    {
        Scanner obj=new Scanner(System.in);
        double G=6.67408e-11;
        double Me=5.972*Math.pow(10,24);       //using pow() of Math class
        double R=6.371*Math.pow(10,6);           //using pow() of Math class
        double h,velocity;
        System.out.println("Enter the orbit altitude in miles");
        h=obj.nextDouble();                        //using nextDouble() of Scanner class
        h=1000*1.60934*h;        //1000 is using to convert km into metre
        velocity=Math.sqrt((G*Me)/(R+h));         //using sqrt() of Math class
        velocity=velocity*2.23694;    //converting m/s into miles/hour
        System.out.println("The orbit speed is "+velocity+" miles/hour");
    }
}

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