00:01
In this question, we have this coffee mug that is 8 cm in diameter.
00:08
And the question says, if you walk at just the right speed of one step per hertz, then this coffee mark, so if this is a coffee mug, the water in it will form a standing wave like this.
00:28
One side will be higher and one side will be lower, just like what this picture looks like.
00:35
And if you walk at one step per hertz, so that's one step per second, so that is a frequency of one hertz, at one hertz, this it will form a standing wave.
00:47
And pretty much for every step you walk, you're introducing this extra force to even make the amplitude of the standing wave larger.
00:59
Because it's almost like you keep pushing it and you make it a forced wave.
01:04
And you're putting external force to it to amplify the wave and eventually the coffee will spill out of the mark...