# 撿鞋運動

:::spoiler code

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib.font_manager import fontManager
plt.rcParams['font.sans-serif'] = ['SimHei'] 
plt.rcParams['axes.unicode_minus'] = False  
fig = plt.figure(figsize=(7,7))
ax1 = fig.add_subplot(1,1,1)
ax2 = fig.add_subplot(2,1,1)
ax3 = fig.add_subplot(3,1,1)
fig.subplots_adjust(hspace=.45)
k = 100
m = 20
w = np.sqrt(k/m)
phi = 2
A = 2
p = 2*np.pi/w
f = 1/p
print("Period:",p,"seconds",sep=" ")
print("f:",f,"Hz",sep=" ")
print("k: ",k,"N/m",sep=" ")
def fun(t):
    global w,phi,A
    return A*np.sin(w*t+phi)
def vel(t):
    global w,phi,A
    return A*w*np.cos(w*t+phi)
def acceleration(t):
    global w,phi,A
    return -A*w**2*np.sin(w*t+phi)
def position(x):
    x1 = x-1
    x2 = x+1
    y1 = 1 
    y2 = -1
    p1 = [x1,y2]
    p2 = [x2,y2]
    p3 = [x2,y1]
    p4 = [x1,y1]
    return [p1,p2,p3,p4]
cnt = 0
xt = [0]
yt = [0]
vy = [0]
acy = [0]
def animate(i):
    global cnt, xt,yt,A,vy,acy
    ax3.clear()
    plt.subplot(311)
    plt.xlim(-3.5,3.5)
    plt.ylim(-2,2)
    plt.xlabel("x")
    plt.ylabel("y")
    plt.title("撿鞋運動")   
    p1 = [position(fun(cnt))[0][0],position(fun(cnt))[0][1]]
    p2 = [position(fun(cnt))[1][0],position(fun(cnt))[1][1]]
    p3 = [position(fun(cnt))[2][0],position(fun(cnt))[2][1]]
    p4 = [position(fun(cnt))[3][0],position(fun(cnt))[3][1]]
    x = [p1[0],p2[0],p3[0],p4[0],p1[0]]
    y = [p1[1],p2[1],p3[1],p4[1],p1[1]]
    linex = [-4,p1[0]]
    liney = [0,0]   
    plt.plot(x,y,lw=3,color="blue")
    plt.plot(linex,liney,color="red",ls=":",lw=3)
    plt.subplot(312)
    xt.append(cnt)
    vy.append(vel(cnt))
    plt.title("速度")
    plt.xlim(0,15)
    plt.ylim(-A*w-0.5,A*w+0.5)
    plt.plot(xt,vy,lw=1,color="gray")
    plt.plot([0,15],[0,0],lw=0.5,color="black")
    plt.subplot(313)
    acy.append(acceleration(cnt))
    plt.title("加速度")
    plt.xlim(0,15)
    plt.ylim(-A*w**2-0.5,A*w**2+0.5)
    plt.plot(xt,acy,lw=1,color="gray")
    plt.plot([0,15],[0,0],lw=0.5,color="black")   
    cnt += 0.1  
ani = animation.FuncAnimation(fig,animate,interval=2)
plt.show()

:::