   Motion in a spiral
  Hi, Im wanting to make some objects spiral into the centre of the screen as time progresses, could somebody give me the equations needed to calculate the acceleration vector to achive this, thanks   
  If you calculate the centripetal acceleration needed to move in a circle at the point the object is at (i.e. specify a constant angular velocity, and then use the current distance between the object and the centre of the spiral as the radius) and then increase the magnitude a bit it will spiral inwards.   