function hideFallenApple(apple) {
    //we need to wait until the apple has fallen down
    //so we will use this setTimeout function to wait and the hide the apple
    setTimeout(function () {
        apple.style.display = 'none';
        //call the function that will move the apple to top
        //and display it again
        restoreFallenApple(apple);
    }, 501);
}
Hides the provided element by changing the display property.
@param {HTMLElement} apple