Ответ учителя по предмету Физика
1)
L=10 км=1 10⁴ м масса провода: m=dV=dLs;
R=10 Ом d-плотность; L-длина; s-площадь сечения;
d=8,5 г/см³=8,5 10³ кг/м³ s-найдем из ф-лы сопротивления;
ρ=1,8 10⁻⁸ Ом м R=ρL/s; s=ρL/R;
m-? s=1,8 10⁻⁸1 10⁴/10=1,8 10⁻⁵ м²
m=8,5 10³*1 10⁴1,8 10⁻⁵=15,3 10² кг=1530 кг
Ответ: m=1530 кг.
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