Rain Drop Terminal Velocity

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace RainDrop001
{
    class Program
    {

        static double Drag(double velocity, double diameter) // COMPUTE AIR DRAG
        {
            double area = Math.PI * Math.Pow(diameter / 2, 2);
            //F = .5 * density_of_air * velocity^2 * drag_coef * area
            return .5 * 1.225 * Math.Pow(velocity, 2) * .47 * area * Math.Sign(velocity);
        }

        static void Main(string[] args)
        {







            for (double d = 0.01; d < 5; d += .01)
            {

                double height = 500;        // initial height
                double diam = d * 0.001;        // diameter of rain drop 
                double mass = ((4 / 3) * Math.PI * Math.Pow(diam / 2, 3)) * 1000;

                double v = 0;               // initial velocity

                double dt = 0.0001;         // delta time

                while (height > 0)
                {
                    double a = (-Drag(v, diam) / mass) - 9.8; // calculate acceleration
                    v += a * dt;
                    height += v * dt;

                }


                //File.AppendAllText(@"C:\Users\Rostislav\Desktop\raindrop.txt", d.ToString() + ", " + Math.Round(-v * 2.23694, 2).ToString() + Environment.NewLine);

                Console.ForegroundColor = ConsoleColor.Green;
                Console.WriteLine("DIAMETER (mm): " + d);
                Console.WriteLine("SPEED (mph): " + Math.Round(v * 2.23694, 2));
                Console.WriteLine("ENERGY (Joules): " + .5 * mass * Math.Pow(v,2));
                Console.WriteLine();

            }
            Console.WriteLine("DONE.");
            Console.ReadLine();
        }
    }
}