electric.py 文件源码

def ondraw(self):

        # Calculate electric force
        sk = self.sketch
        dr = delta(self.pos, sk["blue"].pos)
        r = hypot(*dr) / sk.scale / 100
        F = delta(dr, mag = 8.99e-3 * sk.q1 * sk.q2 / (r * r))

        # Add electric plus gravitational forces 
        F = F[0], F[1] + sk.mass * 9.81e-3

        # Tangential acceleration
        s = sk["string"]
        u = s.u
        t = 1 / sk.frameRate
        F = (F[0] * u[1] - F[1] * u[0]) / (sk.mass / 1000) * (sk.scale / 100) / t ** 2
        ax, ay = F * u[1], -F * u[0]

        # Kinematics
        v1x, v1y = tuple(0.95 * v for v in self.vel)
        v2x = v1x + ax * t
        v2y = v1y + ay * t
        self.vel = v2x, v2y
        x, y = self.pos
        x += (v1x + v2x) * t / 2
        y += (v1y + v2y) * t / 2
        x, y = delta((x,y), s.pos, 20 * sk.scale)
        self.pos = s.pos[0] + x, s.pos[1] + y
        s.__init__(s.pos, self.pos)

        # Protractor
        if s.u[1] > 0:
            a = round(2 * degrees(asin(s.u[0]))) / 2
            a = "Angle = {:.1f}° ".format(abs(a))
        else: a = "Angle = ? "
        sk["angle"].config(data=a)