Nothing special but something that i thought might be useful for some of you.
I made a little adaption to the first traer physic example sketch. http://murderandcreate.com/physics/

move the pendulum by moving the sketch window itself .

Have fun.

1. 
   import traer.physics.*;
   ParticleSystem physics;
   
   Particle p;
   Particle anchor;
   Spring s;
   int mX;
   int mY;
   int pX;
   int pY;
   float velX;
   float velY;
   
   
   void setup()
   {
     size( 400, 400 );
     smooth();
     fill( 0 );
     ellipseMode( CENTER );
   background(255);
     physics = new ParticleSystem( 0, 0.05 );
   
   
    
     p = physics.makeParticle( 1.0, width/2, height/2, 0 );
     anchor = physics.makeParticle( 1.0, width/2, height/2, 0 );
     anchor.makeFixed();
     s = physics.makeSpring( p, anchor, 0.01, 0.051, 0 );
     mX = 0;
     pX = 0;
     mY = 0;
     pY = 0;
   }
   
   
   void draw(){
   // 
      fill(255,30);
      rect(0,0,width,height);
     
     physics.tick();
   
     mX = frame.getLocation().x;
     mY = frame.getLocation().y;
   
     velX = (mX-pX)/15.0;
     velY = (mY-pY)/15.0;
    
     p.velocity().add( -velX,-velY,0 );
    
     println(velX);
    
   fill(0,210);
   noStroke();
   
     line( p.position().x(), p.position().y(), anchor.position().x(), anchor.position().y() );
     ellipse( anchor.position().x(), anchor.position().y(), 5, 5 );
     ellipse( p.position().x(), p.position().y(), 10, 10 );
    
     pX = mX;
     pY = mY;
   }