code: @Pure
  	@Inline(value = "PhysicsUtil.getPhysicsEngine().acceleration(($1), ($2), ($3))",
  			imported = {PhysicsUtil.class})
  	public static double acceleration(
  			double previousSpeed,
  			double currentSpeed,
  			double dt) {
  		return engine.acceleration(previousSpeed, currentSpeed, dt);
  	}
docs: Replies the new  acceleration according to a previous
  velocity and a current  velocity, and given time.
  
  <p><code>(currentVelocity - previousVelocity) / dt</code>
  
  @param previousSpeed is the previous  speed of the object.
  @param currentSpeed is the current  speed of the object.
  @param dt is the time
  @return a new acceleration