Participants were 60% slower to consume an alcoholic beverage from a straight glass compared to a curved glass. This effect was only observed for a full glass and not a half-full glass, and was not observed for a non-alcoholic beverage
The researchers who performed the study are psychologists, and they conclude that this may lead to a target for public health intervention – in plain English, it might be a useful method to help fight excessive drinking. I, however, am more interested in the physics of why this might happen. I suspect this may have to do with the curve of the glass providing some extra acceleration from gravity when you lift the glass high enough, which gives me an excuse (not that I really need one) to go into the physics.
When you lift and tilt the glass, you’re basically rotating a system around it’s centre of mass until most of the beer’s mass lies above it. At this point, the force of gravity is obviously going to act on the beer and pull it down into your mouth (or the floor if you’re not careful), and since beer is a fluid with low viscosity (according to this site, it’s 1.8 centiStokes, which translates to 1.8 square millimetres per second; compare that to sea water’s 1.15 cSt), it tends to flow very easily along the glass. This is where my previous point about the curve of the glass comes in: as it flows along the glass, the beer is flowing slightly faster downwards along a glass that curves outwards than a straight glass.
I need a drink – out of a straight glass 🙂