hi,here is my program.
it is my pleasure to help u!
import java.util.Scanner;
public class App {
/**
* @param args
*/
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int time = 0;
do {
System.out.println("Please input a time less than 20 seconds!");
time = s.nextInt();
} while (time >= 20 || time < 0);
System.out.println("The object is at " + (100 - 4.9 * time * time)
+ " meter!");
}
}