## Sunday, October 22, 2017

### Popping Champagne (The Wrong Way)

Over the weekend, for no particular reason, I found myself thinking about the physics of popping a bottle of champagne. I realized that a cork shooting out of a bottle of champagne could be considered an inelastic collision, due to the fact that it is two objects coming apart. In inelastic collisions, momentum is conserved, but energy is not. Because the cork shoots out in one direction, in order for momentum of the system to be conserved, the bottle must theoretically move in the opposite direction. The reason that this is barely noticeable is because of how the mass of a champagne cork is far smaller than that of a bottle of champagne, so to achieve equal momentum as the fast moving cork, the bottle doesn't have to move very much in the opposite direction. This may also be stopped by the person who is holding the bottle anticipating its slight movement backwards.

This is not the only physic phenomenon that occurs within a bottle of champagne. The actual dislodging of the cork out of the bottle requires that unequal forces act on the cork. When a cork is at rest in an unopened bottle, there is pressure acting on the cork from the dissolved CO2 molecules in the champagne. This pressure force is balanced by the static frictional force between the cork and the walls of the bottle, keeping the cork at rest. Once the cork is moved slightly, the frictional force moves to kinetic friction, which is traditionally lower due to the fact that it is easier to keep an object in motion than to put it into motion. The unbalanced forces cause the cork to accelerate and shoot out of the bottle.

So this New Year's Eve when the clock strikes 12:00, make sure to grab a bottle of champagne and a camera to record it being popped, and the immediately upload the video to Tracker in order to determine the speed of the cork leaving the bottle.