[tex]Dane:\\n = 60\\t = 2 \ s\\r = 20 \ cm = 0,2 \ m\\Szukane:\\v = ?\\\\Rozwiazanie\\\\f = \frac{n}{t} = \frac{60}{2 \ s} = 30 \ Hz = 30 \frac{1}{s}\\\\v = \frac{2\pi r}{T}\\\\T = \frac{1}{f}, \ zatem:\\\\v = 2\pi rf\\\\v = 2\cdot3,14\cdot0,2m\cdot30\frac{1}{s}\\\\\boxed{v = 37,68\frac{m}{s}}[/tex]
