Ответ: [tex]T= 2\pi \sqrt{ \frac{l}{g} } [/tex][tex]T _{1} = 2 \times 3.14 \times \sqrt{ \frac{3.9}{9.8} } ≈ 4[/tex] c[tex]T = \frac{t}{n} [/tex][tex]T_2 = \frac{t_2}{n_2} [/tex][tex]t_2 = T_2n_2[/tex][tex]t_2 = 4 \times 17 = 68[/tex] с[tex]t_1 = t_2 = 68[/tex] с[tex]T_1 = \frac{t_1}{n_1} [/tex][tex]T_1 = \frac{68}{68} = 1[/tex] с[tex]T= 2\pi \sqrt{ \frac{l}{g} } [/tex][tex] {T}^{2} = 4 {\pi}^{2} \frac{l}{g} [/tex][tex] {T}^{2} g = 4 {\pi}^{2} l[/tex][tex]l = \frac{ {T}^{2}g }{4 {\pi}^{2} } [/tex][tex]l_1= \frac{ {T_1}^{2}g }{4 {\pi}^{2} } [/tex][tex]l_1 = \frac{ {1}^{2} \times 9.8}{4 \times 3.14 ^{2} } ≈ 0.3[/tex] м