2D Spring

from tkinter import *
import time
import numpy as np
import math
tk=Tk()
WIDTH=500
HEIGHT=500
canvas=Canvas(tk,width=WIDTH,height=HEIGHT)
tk.title('Viscosity')
canvas.pack()
SIDE=200
LENGTH=200
k=100
dt=.0003
vell=[0,100]
velr=[100,-1000]

TL=canvas.create_rectangle(200,300,210,310,fill='blue')
print(canvas.coords(TL))
TR=canvas.create_rectangle(200+SIDE,300,210+SIDE,310,fill='blue')
#BL=canvas.create_rectangle(200,100+SIDE,210,110+SIDE,fill='blue')
#BR=canvas.create_rectangle(200+SIDE,100+SIDE,210+SIDE,110+SIDE,fill='blue')


while True:
    TLTR=(canvas.coords(TR)[0]-canvas.coords(TL)[0],canvas.coords(TL)[1]-canvas.coords(TR)[1])
    accl=np.dot(((np.linalg.norm(TLTR)-LENGTH)*k/np.linalg.norm(TLTR)),(np.dot(TLTR,(1,0)),np.dot(TLTR,(0,-1))))
    accr=-accl
    vell+=accl*dt
    velr+=accr*dt
    canvas.move(TL,vell[0]*dt,vell[1]*dt)
    canvas.move(TR,velr[0]*dt,velr[1]*dt)
    if canvas.coords(TL)[0]<0 or canvas.coords(TL)[2]>WIDTH:
        vell[0]=-vell[0]
    if canvas.coords(TR)[0]<0 or canvas.coords(TR)[2]>WIDTH:
        velr[0]=-velr[0]
    if canvas.coords(TL)[1]<0 or canvas.coords(TL)[3]>HEIGHT:
        vell[1]=-vell[1]
    if canvas.coords(TR)[1]<0 or canvas.coords(TR)[3]>HEIGHT:
        velr[1]=-velr[1]
    tk.update()
    
print(vell)
tk.mainloop()