使用python模拟2D弹性碰撞

Question

我已经在Python 3中编写了一个脚本来模拟二维的弹性碰撞。我不知道我在做什么错，因为当我运行它时，这些球似乎相互粘连，有时会出现毛刺而变成一个球。另外，当单个球撞击屏幕的任何边缘时，它都会弹起，但是当另一个球粘在其上时，它将导致其中一个球从屏幕上脱落。

Eqautions that I used

代码段：

class Particle(Sprite):
    def __init__(self, image):
        super(Particle, self).__init__(image)
        self.Vxi, self.Vyi = random.randint(-3, 3), random.randint(-3, 3)
        self.mass = random.randint(1, 100) / 1000

        self.schedule_interval(self.update, 1/60)

    def update(self, dt):
        self.xpos, self.ypos = self.position

        if self.xpos <= self.width/2 or self.xpos >= scr_width - self.width/2:
            self.Vxi *= -1
        if self.ypos <= self.width/2 or self.ypos >= scr_height - self.height/2:
            self.Vyi *= -1

        for particle in director.scene.children[0][1].particles:
            particle_xpos, particle_ypos = particle.position

            if abs(self.xpos - particle_xpos) <= self.width/2 + particle.width/2:
                if abs(self.ypos - particle_ypos) <= self.height/2 + particle.height/2:
                    xmomentum = (particle.mass * particle.Vxi) + (self.mass * self.Vxi)
                    ymomentum = (particle.mass * particle.Vyi) + (self.mass * self.Vyi)
                    Vxf = (xmomentum - particle.mass * (self.Vxi - particle.Vxi)) / (particle.mass + self.mass)
                    Vyf = (ymomentum - particle.mass * (self.Vyi - particle.Vyi)) / (particle.mass + self.mass)
                    self.Vxi = Vxf
                    self.Vyi = Vyf

        self.xpos += self.Vxi
        self.ypos += self.Vyi
        self.position = self.xpos, self.ypos