Every morning it happens. There, on the floor at work or home—or on your shoe—is a splat of coffee. Or tea. Or any other beverage you may enjoy as a way to yay up your day. It seems like an intractable problem. Sure you could use a cup with a lid, but that’s a cop out. Instead, try this cool, educational solution: an “unspillable” cup that cancels out the resonate frequencies of itself and the person holding it as they walk.
The Action Lab, a science education channel on YouTube, recently posted the above snippet. The video shows the final product of The Action Lab’s original video showing how to build the cup. That one went viral in 2018, because, we can only assume, everyone who drinks from a mug encounters this problem.
In the 2018 video (below), The Action Lab’s host describes how he tackled the physics challenge. The central problem, he notes, is that when a person walks with a mug, the frequencies of their hand moving and the liquid in the mug moving coincide. I.e. they resonate.
As the host notes, this resonance is a problem, as this means when somebody walking with a mug in their hand pushes that hand forward, they tug on the liquid in the cup. That liquid is already moving backward anyway. Likewise, when a person moves their hand backward, they increase the wave size of the liquid in the mug as it moves toward the front lip. The result is a whole lot of splashing.
This unspillable cup—we see it working best as a mug—works via a base connected to a tether that a person holds. The contraption, which itself bobs back and forth as a person’s hand moves, allows the liquid in the mug and the mug itself to move in unison. This, in turn, cancels out the resonate frequency between the liquid in the mug and a holder’s moving hand. And all we can say is: get these things on shelves so we can take drinks upstairs without fear! (Because really, who uses lids?)