The Physics Behind the Design of a Typical Coffee Mug

Madelyn Leembruggen of SciShow explains how the design of typical coffee mugs is questionable at best, particularly since coffee has exactly the same resonance as a person walking. This means that coffee will slosh quite easily if not carried properly and the mug does nothing to stop the sloshing.

The average frequency of a person walking  is typically about 1 – 2.5 steps per second… That’s the exact resonant  frequency of a typical coffee mug! Those small forces, at just  the right time intervals,  make the waves in the mug get taller and taller…Until you’ve got a big stain on your khakis.

Leembruggen also offers some suggestions to keep sloshing down to a minimum.

First, you could change your coffee order. A layer of foam on top of a beverage  efficiently dissipates a lot of sloshing energy,  preventing large waves from building up  and eventually tipping over the edge. That’s why a pint of beer is far less  likely to slosh than a pint of cold brew. …Or, here’s an idea: We could just stop making mugs shaped in the exact way that  causes resonance when we walk.