電荷在電場中的運動作業(HW_charge.py)

這個習題希望同學們能夠利用我們在電學和運動模擬中所學到的經驗，來設計並體驗拉塞福在1909年非常著名的散射實驗，這個實驗被譽稱為20世紀最偉大物理實驗。

GlowScript 3.0 VPython
def EF_point(q,rq,r):
    ke=1.
    rrq=r-rq
    rrq0=mag(rrq)
    E=ke*q*rrq/rrq0**3
    return E    
q=79; rq=vec(0,0,0)
scene = display(width=1000, height=700, center=vec(0, 0, 0))
Xaxis=arrow(pos=vec(-4,0,0),axis=vec(8,0,0),shaftwidth=0.01, headwidth=0.02)
Yaxis=arrow(pos=vec(0,-1,0),axis=vec(0,2,0),shaftwidth=0.01)
charge = sphere(pos=rq, radius=0.05, color=color.red)
Na=21; qa=2.; ma=4.; xa=-2; va=60; Ly=0.2; Ly2=Ly/2; dy=Ly/Na
qc=[qa for i in range(Na)]
es = [sphere(pos=vec(-2,-Ly2+dy*i,0), radius=0.03, color=vec(0.5+0.5*random(),0.5+0.5*random(),0.5+0.5*random()), 
    make_trail=True) for i in range(Na)]
for i in range(Na):
    es[i].v=vec(va,0,0)
t=0.; dt=0.0002; NR=int(1/dt)
labva='va={:04.1f}'.format(va)
label(text=labva,pos=vector(-2,2,0))
print_options(width=1000, height=100)
print('q=',q,'  rq=',rq,'  Na=',Na,'  qa=',qa,'  ma=',ma,'  xa=',xa,'  va=',va,'  Ly=',Ly)
scene.waitfor('click')
while t < 10:
    rate(NR/40)
    for i in range(Na):
        if(mag(es[i].pos) > 2.2): break
        E=EF_point(q,rq,es[i].pos)
        #es[i].v+=  
        es[i].pos+=rs[i].v*dt
    t+=dt