Какова сила сопротивления резанию строгального станка мощностью 10 квт, если скорость резания 0,75 м/с, а кпд станка = 75% ? в ответе должно получиться 10 кн; нужно решение
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The fireman is a very interesting and dangerous profession.when the fireman helping people, he risks his life.this people must have good physical parameters.and he must be brave and don't afraid come in the burning house. this profession very intense because for fireman depending life of the peoples,therefore he must be responsible and was good reaction.as this profession was a good paying maybe this is one of its pluses. the firemans was respecting and considering a hero.they was authority at many people
Pз = 10 кВт = 10000 Вт
v = 0,75 м/c
η = 75 % = 0,75
Fсопр - ?
Решение:
По второму закону Ньютона
ma(вектор) = Fсопр(вектор) + Fтяги(вектор)
Так как ускорение равно нулю, а сила тяги и сила сопротивления противонаправленные, то получим
Fсопр - Fтяги = 0
Fсопр = Fтяги
Полезная мощность
Pп = Aп / t = (Fтяги · S) / t = Fтяги · v = Fсопр · v
КПД
η = Pп / Pз ⇒ Pп = η · Pз
Приравняем полезную мощность
Fсопр · v = η · Pз
Выразим силу сопротивления
Fсопр = η · Pз / v
Подставим данные значения
Fсопр = 0,75 · 10000 / 0,75 = 10000 Н = 10 кН
ответ: 10 кН