问题: 机械钟的时针和分针,都是围绕钟的中心轴顺时针旋转的。如果我们以时针的针尖为参考系,那么分针的针尖围绕时针的针尖运动轨道,是不是外摆线?
答:这个问题很有趣。下面写出其参数方程,并做出图形。
动画的Maple程序(帧数:540):
with(plots): with(plottools):
a:=1:b:=0.2:k:=60:
x:=t->a*cos(-t+Pi/2)+b*cos(-k*t+Pi/2);
y:=t->a*sin(-t+Pi/2)+b*sin(-k*t+Pi/2);
K:=540: for i from 1 to K do
ti:=i*2*Pi/K:
quxian[i]:=plot([x(t),y(t),t=0..ti],color=gray):
shizhen[i]:=plot([[0,0],[a*cos(-ti+Pi/2),a*sin(-ti+Pi/2)]],color=blue,thickness=3):
fenzhen[i]:=plot([[x(ti),y(ti)],[a*cos(-ti+Pi/2),a*sin(-ti+Pi/2)]],color=black,thickness=3):
dongyuan[i]:=circle([a*cos(-ti+Pi/2),a*sin(-ti+Pi/2)],b,color=red,thickness=2) od:
quxian:=display(seq(quxian[i],i=1..K),insequence=true):
shizhen:=display(seq(shizhen[i],i=1..K),insequence=true):
fenzhen:=display(seq(fenzhen[i],i=1..K),insequence=true):
dongyuan:=display(seq(dongyuan[i],i=1..K),insequence=true):
yuan:=circle([0,0],a,color=brown,thickness=3):
display(yuan,dongyuan,shizhen,quxian,fenzhen,scaling=constrained,tickmarks=[0,0]);
图形的Maple程序:
with(plots):
a:=1:b:=1.2:k:=60:
x:=t->a*cos(-t)+b*cos(-k*t);
y:=t->a*sin(-t)+b*sin(-k*t);
curve:=plot([x(t),y(t),t=0..2*Pi],thickness=2):
display(curve,scaling=constrained,tickmarks=[4,4]);
动画的Maple程序:
with(plots):
a:=1:b:=0.1:k:=60:
x:=t->a*cos(-t+Pi/2)+b*cos(-k*t+Pi/2);
y:=t->a*sin(-t+Pi/2)+b*sin(-k*t+Pi/2);
K:=360:
for i from 1 to K do
ti:=i*2*Pi/K:
quxian[i]:=plot([x(t),y(t),t=0..ti],thickness=2):
shizhen[i]:=plot([[0,0],[a*cos(-ti+Pi/2),a*sin(-ti+Pi/2)]],color=blue,thickness=3):
fenzhen[i]:=plot([[x(ti),y(ti)],[a*cos(-ti+Pi/2),a*sin(-ti+Pi/2)]],color=gray,thickness=3) od:
quxian:=display(seq(quxian[i],i=1..K),insequence=true):
shizhen:=display(seq(shizhen[i],i=1..K),insequence=true):
fenzhen:=display(seq(fenzhen[i],i=1..K),insequence=true):
display(quxian,shizhen,fenzhen,scaling=constrained,tickmarks=[5,3]);
成都大熊猫基地 2012.4.6
评论