#!/usr/bin/env pltthon3
# -*- coding: utf-8 -*-
"""
ENGG1811, Lecture 3, In-lecture project template

"""

# Import 
import math
import matplotlib.pyplot as plt 

# Constants
g = 9.81 # acceleration due to gravity in kg/s/s 

# Define a function to compute the free fall speed 
def free_fall(t,mass,drag):
    # To compute the freefall speed
    speed = g * mass / drag * (1 - math.exp(-drag*t/mass))
    return speed
    
    
# Problem parameters
mass = 70       # Mass of the object in kg  
drag = 12.5     # Drag coefficient for air in kg/s
 

# Test the function free_fall
print('Speed at time 5',free_fall(5,mass,drag)) # Expect 32.4
print('Speed at time 10',free_fall(10,mass,drag)) # Expect 45.7

# To create a list of times 
# [0,0.5,1,1.5 ...,40] 

# range     0,   1, 2,   3, 4,  ...,80  <-- given 
# time_list 0, 0.5, 1, 1.5, 2       40  <-- derive 
time_list = []
for k in range(81):
    time = k / 2
    time_list.append(time)


# To compute the list of speeds 
speed_list = []    
for t in time_list:
    speed_at_time_t = free_fall(t, mass, drag)
    speed_list.append(speed_at_time_t)    

# To plot the graph 
# Note: You need to edit the line with plt.plot
# To uncomment a block of text, use the Edit menu and choose
# Comment/Uncomment 
fig1 = plt.figure() 
plt.plot(time_list,speed_list,'x') # <- need editing 
plt.xlabel('time [seconds]')
plt.ylabel('speed [m/s]')
plt.title('Free fall speed')
#plt.grid()
#plt.show()