Question

怎么用java模拟小球的圆周运动？

用小应用程序吧，用什么算法呢？不知道代码该怎么写

Answer 1

//简单的做个
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Circle extends JFrame {

public Circle(){
super();
CirclePanel panel=new CirclePanel();
add(panel, "Center");
setSize(500, 500);
setVisible(true);
}

public static void main(String[] args) {
new Circle();
}

class CirclePanel extends JPanel{
public static final double PI=Math.PI;
private int degree=0;
private int axisx;
private int axisy;
public CirclePanel(){
setSize(500, 500);
axisx=getWidth()/2;
axisy=getHeight()/2;
setVisible(true);
Timer timer=new Timer(10,new TimerListener());
timer.start();
}

@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.fillRect(axisx, axisy, 2, 2);
g.drawOval((int)(axisx-100+5), (int)(axisy-100+5), 200, 200);
g.fillOval(-(int)(100*Math.sin(PI*degree/180))+axisx,
(int)(100*Math.cos(PI*degree/180))+axisy, 10, 10);

}

class TimerListener implements ActionListener{

public void actionPerformed(ActionEvent e) {
degree += 1;
repaint();
}
}
}
}

Answer 2

圆周运动的速度是每时每刻都在改变的，注意是速度不是速率，要改变速度就要给它一个外力，也就是我们一般说的向心力。要是没有这个力它的速度就不会改方向，沿直线走，所以你会感到它向外跑。