The video was taken in SLO-MO mode, at 240 frames per second.
To step one frame at a time on a laptop, pause the video and then type period (.) to step forward or comma (,) to step backwards.
I find that this one-frame feature is not very consistent across platforms. I usually have to press the period key twice for every frame. On my laptop it sometimes jumps two frames, but on my windows desktop and my iMac desktop it is reliably 2 key strokes per frame.
I don't know how to step one frame at a time on my iPhone. Let the class know if you figure out how to do this!
I am not sure, but I assume that the playback is at 30 frames per second on YouTube. If you cannot step a single frame, try to estimate the speed by timing the time to travel 10 cm (or 30 cm) in slow motion.