如何将力应用于多个对象？

import pygame
import sys

# 初始化Pygame
pygame.init()

# 设置窗口大小
screen = pygame.display.set_mode((800, 600))

# 定义颜色
WHITE = (255, 255, 255)

# 定义物体类
class Object:
    def __init__(self, x, y, mass):
        self.x = x
        self.y = y
        self.mass = mass
        self.vx = 0
        self.vy = 0

    def apply_force(self, fx, fy):
        ax = fx / self.mass
        ay = fy / self.mass
        self.vx += ax
        self.vy += ay

    def update(self):
        self.x += self.vx
        self.y += self.vy

# 创建物体
objects = [Object(100, 100, 1), Object(200, 200, 1), Object(300, 300, 1)]

# 主循环
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    # 清屏
    screen.fill(WHITE)

    # 应用力
    for i in range(len(objects)):
        for j in range(i + 1, len(objects)):
            dx = objects[j].x - objects[i].x
            dy = objects[j].y - objects[i].y
            distance = (dx ** 2 + dy ** 2) ** 0.5
            force = 0.1 / distance
            fx = force * dx / distance
            fy = force * dy / distance
            objects[i].apply_force(fx, fy)
            objects[j].apply_force(-fx, -fy)

    # 更新物体位置
    for obj in objects:
        obj.update()

    # 绘制物体
    for obj in objects:
        pygame.draw.circle(screen, (0, 0, 255), (int(obj.x), int(obj.y)), 10)

    # 更新屏幕
    pygame.display.flip()