Shut the Door

You are sitting on your bed in your dorm room, and suddenly you hear the voice of your ex coming down the hall. You really want to avoid any contact (you broke things off a week ago), and so you want to shut the door. But you don't have time to get up and shut it and act like it wasn't on purpose. You need something fast. Sitting beside you, you happen to have a superball and a ball of clay of roughly equal mass that you fidget with when you're studying on your bed. What do you do?

Explain your answer and show why you chose one and not the other.