阻尼振动.cpp

物理程序

#include <a:ccbp.h>

void main()
{
 double y,t,w0,w,b;
 char c,m[20];
 int N=1;
 int gd=DETECT,gm;
 initgraph(&gd,&gm,"e:\\borlandc\\bgi");
 setbkcolor(3);
 setcolor(5);
 b=50;
 w0=50;
 do
   {
    cleardevice();
    sprintf(m,"b=%d,w=%d",(int)b,(int)w0);
    setcolor(4);
    outtextxy(250,450,m);
    setcolor(13);
    outtextxy(530,470,"ESC-exit");
    outtextxy(500,450,"Up-w+ Down-w-");
    outtextxy(500,460,"Right-b+ Left-b-");
    t=0;
    setlinestyle(0,0,1);
    coordc(40,350,590,0,590,1);
    coordc(40,460,450,90,450,1);
    setcolor(4);
    outtextxy(615,355,"t");
    outtextxy(45,20,"X");
    setcolor(5);
    setlinestyle(0,0,3);
    if(fabs(b*b-w0*w0)<0.1)
      {
       outtextxy(200,430,"x=(c1+c2*t)*exp(-b*t)");
       do
	 {
	  y=(300+10*0.01*t)*exp(-b*0.01*t);
	  if(t==0)
	    moveto(40,350-y);
	  else
	    lineto(40+30*t,350-y);
	 }while((t=t+0.1)<19);
      }
    else
      if(b*b>w0*w0)
	{
	 outtextxy(100,430,"x=c1*exp(-(b-sqrt(b*b-w*w))*t)+c2*exp(-(b+sqrt(b*b-w*w))*t)");
	 do
	  {
	   y=150*exp(-(b-sqrt(b*b-w0*w0))*0.01*t)+150*exp(-(b+sqrt(b*b-w0*w0))*0.01*t);
	   if(t==0)
	     moveto(40,350-y);
	   else
	     lineto(40+30*t,350-y);
	  }while((t=t+0.1)<19);
	}
      else
	if(b*b<w0*w0)
	  {
	   outtextxy(200,430,"x=A*exp(-b*t)*cos(w*t)");
	   w=sqrt(w0*w0-b*b);
	   do
	    {
	     y=300*exp(-b*t*0.01)*cos(w*t*0.01);
	     if(t==0)
	       moveto(40,350-y);
	     else
	       lineto(40+30*t,350-y);
	    }while((t=t+0.1)<19);
	  }
   c=getch();
   if(c==75)
     b=(b-2)<0?0:(b-2);
   else
     if(c==77)
       b=b+2;
     else
       if(c==72)
	 w0=w0+2;
       else
	 if(c==80)
	   w0=(w0-2)<0?0:(w0-2);
	 else
	   if(c==27)
	     N=0;
  }while(N);
 closegraph();
}