5_6_Phase_Plot.py

import numpy as np
import matplotlib.pyplot as plt
import math
from scipy.integrate import odeint

M=2.394
m=1
g=9.81

def Atwood(y,t,M,m,g):

    theta, omega, radius, Rho = y
    
    #dydt = [omega, (1/radius)*(-g*(np.sin(theta))-2*(Rho*omega)),Rho, (1/(M+m))*(m*radius*(omega^2)-M*g+m*g*(np.cos(theta)))]
    dydt = [omega, (1/radius)*(-g*(np.sin(theta))-2*(Rho*omega)), Rho, (1/(M+m))*(m*radius*(omega**2)-M*g+m*g*(np.cos(theta)))]
    
    return dydt
                           
#y0=[theta, change in theta, radius, change in radius]
y0 = [np.pi/2,0 ,1,0]
#time points
t = np.linspace(0,100,1000000)
#Solving the ODE
sul = odeint(Atwood, y0, t, args=(M,m,g))


plt.plot(sul[:,0], sul[:,1], 'r')
plt.ylabel('Angular velocity')
plt.xlabel('Angular displacement')
plt.title('Fig 5.6 - Phase Plot')
plt.grid()
plt.show()