Flatten an Index Card

Challenge your students (or family members or friends or anyone else you encounter) to find two ways to flatten an index card, without touching it.

To prepare, fold an index card in half and set it on the table to make a tent. 

Your challengee will likely immediately blow on the top of the card to push the middle down.

The challenge comes in finding a second way to accomplish the task. 

It's time to put your knowledge of Bernoulli and air pressure to work!  By blowing under the card, you'll move those air molecules out of the way, allowing the air molecules on top of the card to push the card down.