Answer:
What is something yet nothing, but if you fill it up it will disappear?
Defends your noggin from the hard pavement
Where is the ocean deepest?
This sparkling globe can float on water. It is light as a feather, but ten giants can't pick it up.
It belongs to you, but other people use it more than you do. What is it?
As round as an apple. As deep as a cup. All the king's horses can't pull it up.