class Sim{
	public double px=0.0;
	public double py=0.0;
	public double v=1.0;
	public double myu=0.3;
	public double alpha=30;
	
	public Sim(double x0,double y0,double v0){
		init(x0,y0,v0);
	}
	public void init(double x0,double y0,double v0){
		px=x0;
		py=y0;
		v=v0;
	}
	public void setMyu(double myu0){
		myu=myu0;
		if(myu>1) myu=1.0;
		if(myu<0) myu=0.0;
	}
	public double dx_dt(){
		return Math.cos(alpha*3.14159/180)*(v+dv_dt());
	}
	public double dy_dt(){
		return Math.sin(alpha*3.14159/180)*(v+dv_dt());
	}
	public double dv_dt(){
		if(9.8065*Math.sin(alpha*3.14159/180)-myu*9.8065*Math.cos(alpha*3.14159/180)<0)
			return 0;
		else
			return 9.8065*Math.sin(alpha*3.14159/180)-myu*9.8065*Math.cos(alpha*3.14159/180);
	}
	public void one_step(double dt){
		px=px+dt*dx_dt();
		py=py+dt*dy_dt();
		v=v+dt*dv_dt();
	}
}