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I want to implement a ball that is bounding continuously.If you execute the following code, the ball bounces to a position higher or lower than the position where it started dropping.Is this an error from the calculation? Or is the implementation wrong?class ViewController: UIViewController { @IBOutlet weak var imageView: UIImageView! var dynamicAnimator: UIDynamicAnimator! override func viewDidLoad() { super.viewDidLoad() } @IBAction func fallButtonTapped(_ sender: Any) { let gravityBehavior = UIGravityBehavior(items: [imageView]) dynamicAnimator = UIDynamicAnimator(referenceView: self.view) dynamicAnimator.addBehavior(gravityBehavior) let collisionBehavior = UICollisionBehavior(items: [imageView]) collisionBehavior.translatesReferenceBoundsIntoBoundary = true dynamicAnimator.addBehavior(collisionBehavior) let dynamicItemBehavior = UIDynamicItemBehavior(items: [imageView]) dynamicItemBehavior.elasticity = 1.0 dynamicItemBehavior.resistance = 0.0 dynamicItemBehavior.friction = 0.0 dynamicAnimator.addBehavior(dynamicItemBehavior) } }