模拟双摆在重力场中的运动。摆杆由两段长分别为l1和l2 的刚性杆构成，质量分别为m1和m2 ，两杆之间连接无摩擦的铰链，摆锤的质量为M。可研究（不要求每个部分完全分析清楚）：1.同样的杆长不同的初始位置摆的运动2.杆长改变时摆的运动3.改变摆和杆的质量对摆运动的影响4.考虑空气阻尼的影响-Simulate double pendulum motion in the gravitational field. The pendulum consists of two lengths of l1 and l2 of the rigid rod constituted of masses m1 and m2, the connection between two friction hinge, the pendulum mass M. May study (full analysis of each part is not required to clear): 1. Similarly different initial positions rod length pendulum 2. Rod length changes pendulum 3. Alter the quality of the pendulum and rod pendulum movement of four. consider the impact of air damping