## 學習目標
利用while迴圈改變物體的位置，使物體移動，並繪製出物體移動時的x-t、v-t、a-t圖。

## 課堂練習
有一顆球的初速為(2,0,0)，加速度為(-1,0,0)，模擬其在五秒內的運動，並繪製出x-t、v-t、a-t圖。

### 成果
影片連結：https://youtu.be/231jYHmZwaI

### 程式碼

Web VPython 3.2
size = 0.5 #定義變數，用來描述球體的大小
scene = canvas(width = 600, height = 400, centr = vector(0,0,0), background = vector(0.9,0.9,0.9), align = 'left')  #調整視窗顯示的特性

#畫出座標軸
x = arrow (pos = vector(0,0,0) , axis = vector (1,0,0) , shaftwidth = 0.02, color = color.black)
y = arrow (pos = vector(0,0,0) , axis = vector (0,1,0) , shaftwidth = 0.02, color = color.black)
z = arrow (pos = vector(0,0,0) , axis = vector (0,0,1) , shaftwidth = 0.02, color = color.black)

ball = sphere(pos = vector(0,0,0) , radius = size , color = color.magenta, v = vector(2,0,0), a = vector(-1,0,0)) #賦予 ball 各種屬性

pic_1 = graph(title = 'x vs t', width = 300, height = 300, xtitle = 't', ytitle = 'x', 
foreground = color.black,background = color.white,xmax = 5, xmin = 0, ymax = 5, ymin = -5, align = 'right')
x_t = gcurve(color = color.blue) #繪製x-t圖

pic_2 = graph(title = 'v vs t', width = 300, height = 300, xtitle = 't', ytitle = 'v', 
foreground = color.black,background = color.white,xmax = 5, xmin = 0, ymax = 5, ymin = -5, align = 'right')
v_t = gcurve(color = color.red) #繪製v-t圖

pic_3 = graph(title = 'a vs t', width = 300, height = 300, xtitle = 't', ytitle = 'a', 
foreground = color.black,background = color.white,xmax = 5, xmin = 0, ymax = 5, ymin = -5, align = 'right')
a_t = gcurve(color = color.green) #繪製a-t圖

dt = 0.001
t = 0;

while t <= 5:
    rate(1000) #動畫播放速率與影格數
    ball.pos = ball.pos + ball.v * dt #迴圈更新物體位置
    ball.v = ball.v + ball.a * dt #迴圈更新物體速度
    t = t + dt
    x_t.plot(pos=(t,ball.pos.x)) #繪製x-t圖
    v_t.plot(pos=(t,ball.v.x)) #繪製v-t圖
    a_t.plot(pos=(t,ball.a.x)) #繪製a-t圖

## 進階問題——學測題的圖像化
質量為 50 kg 的某生站在電梯內的體重計上，電梯原靜止於第一樓層，電梯起動後最初 10 s 體重計的讀數均為 60 kgw，之後 20 s 體重計的讀數均為 45 kgw。若取重力加速度為 10m/s^2^，繪製此題的x-t、v-t、a-t圖。

### 成果
影片連結：https://youtu.be/0H3QEOBNID4
### 程式碼

Web VPython 3.2
size = 0.5 
scene = canvas(width = 600, height = 400, centr = vector(0,0,0), background = vector(0.9,0.9,0.9), align = 'left')

x = arrow (pos = vector(0,0,0) , axis = vector (1,0,0) , shaftwidth = 0.02, color = color.black)
y = arrow (pos = vector(0,0,0) , axis = vector (0,1,0) , shaftwidth = 0.02, color = color.black)
z = arrow (pos = vector(0,0,0) , axis = vector (0,0,1) , shaftwidth = 0.02, color = color.black)

ball = sphere(pos = vector(0,0,0) , radius = size , color = color.magenta, v = vector(0,0,0), a = vector(-1,0,0))

pic_1 = graph(title = 'x vs t', width = 300, height = 300, xtitle = 't', ytitle = 'x', foreground = color.black,
background = color.white,xmax = 30, xmin = 0, ymax = 300, ymin = 0, align = 'right')
x_t = gcurve(color = color.blue)

pic_2 = graph(title = 'v vs t', width = 300, height = 300, xtitle = 't', ytitle = 'v', foreground = color.black,
background = color.white,xmax = 30, xmin = 0, ymax = 30, ymin = 0, align = 'right')
v_t = gcurve(color = color.red)

pic_3 = graph(title = 'a vs t', width = 300, height = 300, xtitle = 't', ytitle = 'a', foreground = color.black,
background = color.white,xmax = 30, xmin = 0, ymax = 5, ymin = -5, align = 'right')
a_t = gcurve(color = color.green)

dt = 0.001
t = 0;

while t <= 30:
    rate(1000)
    if t <= 10:
        ball.a = vector(2,0,0) #在0~10秒的加速度是+2
    else:
        ball.a = vector(-1,0,0) #在10~30秒的加速度是-1
    ball.pos = ball.pos + ball.v * dt
    ball.v = ball.v + ball.a * dt
    t = t + dt
    x_t.plot(pos=(t,ball.pos.x))
    v_t.plot(pos=(t,ball.v.x))
    a_t.plot(pos=(t,ball.a.x))