"""
Ex 5.9 from A primer on ...
Plot function
y = v0*t-0.5*g*t**2
for t in [0,2*v0/g]
"""

import numpy as np
import matplotlib.pyplot as plt

v0 = 10
g = 9.81

n = 101
t_stop = 2*v0/g

"""
We could use this for-loop to create the t-array, but
the single call to linspace below does the same job:
dt = t_stop/(n-1)
t = []
for i in range(n):
    t.append(dt*i)
t = np.array(t)
"""

t = np.linspace(0,t_stop,n)

y = v0*t - 0.5*g*t**2

plt.plot(t,y)
plt.xlabel('time (s)')
plt.ylabel('height (m)')
plt.savefig('plot.pdf')
plt.show()

"""
Terminal> python plot_ball1.py
Output is a plot
"""