When I walk my kid sometimes I put a cut of coffee in a cupholder attached to the stroller. When I push the stroller over a brick pavement it seems to vibrate vertically. That is enough for the coffee to spill, even if the cup is only 3/4 full. It looked like waves were forming in the cup, beating its forward and backward sides, and they quickly grew large enough to spill.
Thus the question: is it possible to quantitively estimate the size of the waves caused by the vibration, so that one could figure out the level one can safely fill the cup to?