When David rolls it around like this, he's turning the sling around probably at six or seven revolutions per second, and that means that when the rock is released, it's going forward really fast, probably 35 meters per second.
Cando David enrosca as asas así, está xirando a fonda probablemente a seis ou sete revolucións por segundo, o que significa que cando lanzas a roca, esta sairá disparada, probablemente a 35 metros por segundo.