import pylab



m = float(input("Mass of object: ")) #Input Variable
g = 9.81 #Constant
v = float(input("Desired Terminal Speed: ")) #Input Variable
A=(((g-0)*m)/(0.1*v**2))+1 #Finding A using the input variables and constant
k = 0.1*A #Set a value of k using A
Start = float(input("Starting speed of object: ")) #Input Variable
d = 300000
t = 15
dt = t/d #Big step in relation to time, to avoid problems of the tangent being to steep and becoming negative.
print("Parachute must be",A,"meters squared to get the desired terminal speed for that object.")


speed = pylab.zeros(d)
time = pylab.zeros(d)

speed[0] = Start
for i in range(d-1): #Goes through all the steps we set
    speed[i+1] = speed[i] + dt*(g-(k*(speed[i]**2))/m) #Takes speed at point i adds the differntial (Which is negative)
    time[i+1] = time[i]+dt #Adds time


pylab.plot(time,speed) #Plots a time/speed graph for us to look at
pylab.xlabel("time[seconds]")
pylab.ylabel("speed[m/s]")