void rescaleVelocities(double ratio) {
		for (int i = 0; i < numberOfAtoms; i++) {
			Atom a = atom[i];
			a.vx *= ratio;
			a.vy *= ratio;
		}
		if (obstacles != null && !obstacles.isEmpty()) {
			RectangularObstacle obs = null;
			synchronized (obstacles.getSynchronizationLock()) {
				for (int i = 0, n = obstacles.size(); i < n; i++) {
					obs = obstacles.get(i);
					if (obs.isPartOfSystem() && obs.isMovable()) {
						obs.vx *= ratio;
						obs.vy *= ratio;
					}
				}
			}
		}
	}