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
0,366 кг
Объяснение:
Дано:
m₁ = 5 кг
с₁ = 4200 Дж/(кг·К)
t₁ = 20⁰C
m₂ = 10 кг
с₂ = 500 Дж/ (кг·К)
t₂ = 500⁰C
t₀ = 100°C
Δm - ?
1)
Сталь отдает количество теплоты:
Q₂ = m₂·c₂·(t₂-t₁) = 10·500·(500-20) ≈ 2,2·10⁶ Дж = 2,4 МДж
2)
Это количество теплоты пойдет на образование пара и на нагревание воды:
Q = r·Δm = 2,3·10⁶·Δm
Q₁ = c₁·(m₁-Δm)·(t₀-t₁) = 4200·(5-Δm)·(100-20) =
4200·(5-Δm)·(100-20) = (5-Δm)·0,336 МДж
3)
По закону сохранения энергии:
Q₂ = Q+Q₁
2,4 = 2,3·Δm+(5-Δm)·0,336
2,4 = 2,3·Δm+1,68-0,336·Δm
0,72 = 1,964·Δm
Δm = 0,72/1,964 ≈ 0,366 кг