Project X19: Conclusions
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The purpose of our project was to capture the different stages of a plate of ice being shattered by a high speed pellet. We expected that as the pellet passed through, the force it created would burst the plate into a cone shaped pattern of fragments on both sides, much like famous photos of bullets piercing apples.
Much of our setup was improvised from materials found on the physics floor. These materials ranged from mouse pads, physics books, ziploc lids, and even dumbwaiter counterweights left over from the school's conversion from a hospital.
Our final photos had many surprises. Along with the typical cone burst, we found several phenomenon we didn't expect. One was a cylindrical pattern in the shatter for a brief time after the pellet strike. This cylinder shape eventually collapsed into a cone. Several of our theories for this phenomenon are:
-The ice follows the shape of the slipstream of the bullet, which is cylindrical just behind the bullet and fans out as the air settles. This only occurs with a sub-sonic pellet, where as famous apple photos use super-sonic cone shaped bullets. (This is our most likely theory)
-The area of the ice that the bullet pulverizes is pushed away from the ice perpendicular to the surface (This can be seen in photos where the ice is clamped in at a non-vertical angle). This could possibly be a force created by the ice as a whole in opposition to the pellet, which also pushed the pulverized pieces of ice on an outward path perpendicular to it
Another phenomenon we noticed was a release of what appears to be liquid or even vapor just around the impact point. This phenomenon is much easier to explain with a little chemistry knowledge. As pressure is applied to solid H2O (i.e. Ice), the melting/freezing point rises. A bullet traveling at two-thirds the speed of sound impacting with a plate of ice is an obvious case of pressure applied to ice, explaining the release of liquid at the impact site. To aid this process, some sheets of ice were already melting before being shot, producing a thin layer of water on the surface. As for the source of the vapor, we believe the sudden acceleration of the water molecules being pushed away from the ice simply causes them to disassociate from each other, producing a vapor.
Overall, our project was a definite success. Not only did we capture images of our subject, we discovered several completely unexpected phenomenon, one of which deals with the unique chemical properties of H2O.