Stabbing a Potato

The other weekend my two daughters, wife, and I had a fun afternoon filled with science experiments.  The first required straws and a potato.

In this experiment we stabbed standard straws into a raw potato.  The experiment part of this comes into play when we set out to determine which style of "stab" sends the straw deepest into the potato.  We first stabbed the potato with both ends of the straw open.  We then stabbed the potato while holding a thumb over one end of the straw.  There is a notable difference in how deep the straw goes.

When the end of the straw is open, the air in the straw is pushed out the top when the other end enters the potato.  If your thumb is covering the open end, the air isn't pushed out and as a result the straw will penetrate deeper into the potato.  Why?   Because the air inside has no place to go and pushes into the potato along with the straw.

This is a fun little experiment that my daughters loved.  My two year old didn't care much about the science, but she sure had fun stabbing potatoes!