n = 152
t = 1 min = 60 s
f = \frac{n}{t}
f = 152 /60 s
f = 2,53 \frac{1}{s} = 2,53 Hz
T = \frac{1}{f}
T = 1 / 2,53 1/s
T \approx0,4 s
g = 9,81 m/s^2
l = ?
T = 2\pi \sqrt{\frac{l}{g} ; podnoszę obustronnie do kwadratu:
T^2 = 4 pi^2 * \frac{l}{g}
T^2*g = 4 pi^2 * l
l = \frac{T^2 *g}{4pi^2}
l = (0,4s)^2 * 9,81 m/s^2 : 4*(3,14)^2
l = 0,16 s^2 * 9,81 m/s^2 : 39,4
l = 1,57 m : 39,4
l = 0,04 m