code: @Pure
  	@Inline(value = "PhysicsUtil.getPhysicsEngine().speed(($1), ($2))",
  			imported = {PhysicsUtil.class})
  	public static double speed(double movement, double dt) {
  		return engine.speed(movement, dt);
  	}
docs: Replies the new  velocity according to a previous velocity and
  a mouvement during a given time.
  
  <p><code>velocity = movement / dt</code>
  
  @param movement is the movement distance.
  @param dt is the time
  @return a new speed