spring wont oscillate vpython

Question

from __future__ import division, print_function
from visual import *
scene.width = 400
scene.height = 760
## constants and data
g = 9.8
mball = 0.03
L0 = 0.26
ks = 1.8
sf = .5
sf2 = 3

#Graphs


## objects (origin is at ceiling)
ceiling = box(pos=vector(0,0,0), length=0.2, height=0.01, width=0.2)
ball = sphere(pos=vector(0,-0.3,0), radius=0.025, color=color.orange)
spring = helix(pos=ceiling.pos, axis=ball.pos-ceiling.pos,color=color.cyan, thickness=.003, coils=40, radius=0.010)
#more constants
Lvec= (ball.pos-ceiling.pos)
Lhat = Lvec / mag(Lvec)
## initial values
pball = mball*vector(0,0,0)
Fgrav = mball*g*vector(0,-1,0)
t = 0
deltat = .01
Fspring = -ks*ball.pos

#arrow vectors
Fharr = arrow(pos=ball.pos, axis=vector(0,0,0), color=color.green) #parallel
Ftarr = arrow(pos=ball.pos, axis=vector(0,0,0), color=color.blue) #perpendicular
parr = arrow(pos=ball.pos, axis=vector(0,0,0), color=color.magenta)

#improve the display
scene.autoscale = False ## turn off automatic camera zoom
scene.center = vector(0,-L0,0) ## move camera down
#scene.waitfor ('click')

## calculation loop
while t <10:
    rate(100)
    #length of L
    Lmag=abs(Lvec.y)
    Lhat = Lvec / mag(Lvec)
    #spring force
    Fspring = -ks*(mag(Lvec)-L0)*Lhat
    #updating position
    Fnet = Fgrav + Fspring
    pball = pball + Fnet*deltat
    ball.pos = ball.pos + (pball/mball)*deltat
    spring.axis = ball.pos - ceiling.pos
    #perpendicuar and parrellel forces
    phat = pball/mag(pball)
    #parallel
    FH = dot(Fnet,phat)*phat
    #perpendicular
    FT = Fnet - FH
    #updating arrows

    t = t + deltat

here's my code, my spring is suppose to oscillate but it wont. It just shoots straight down and doesn't retract, can anyone help me? I think I need to update the position or something in the while loop so when it reaches 0 momentum at the bottom , it retracts but i dont know how.

Answer 1

您永远不会在循环中更改Lvec，因此它始终具有原始值，即使用ball.pos和ceiling.pos的原始值（ball.pos-ceiling.pos）。