Question

Стальной кубик объёмом V=0,05 м3 остывает от t1=400∘C до t2=200∘C. Определить модуль величины выделившегося количества теплоты. Ответ выразить в МДж, округлив до целых. Плотность стали ρ=7800 кг/м3. Удельная теплоёмкость стали c=500 Дж/(кг⋅∘C).

Answer 1

Q=c*m*Δt
Δt=t2-t1=400-200=200 C
m=ρ*V=7800*0.05=390 кг
Q=500*390*200=39*10^6 Дж    (39 МДж)
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Answer 2

Given information:

- Volume of the steel cube, V = 0.05 m^3 - Initial temperature, t1 = 400°C - Final temperature, t2 = 200°C - Density of steel, ρ = 7800 kg/m^3 - Specific heat capacity of steel, c = 500 J/(kg⋅°C)

Calculation:

To determine the amount of heat released, we can use the equation:

Q = mcΔT

Where: - Q is the heat released (in Joules) - m is the mass of the steel cube (in kg) - c is the specific heat capacity of steel (in J/(kg⋅°C)) - ΔT is the change in temperature (in °C)

To find the mass of the steel cube, we can use the equation:

V = m/ρ

Where: - V is the volume of the steel cube (in m^3) - m is the mass of the steel cube (in kg) - ρ is the density of steel (in kg/m^3)

Substituting the given values:

0.05 = m/7800

Solving for m:

m = 0.05 * 7800 = 390 kg

Now we can calculate the change in temperature:

ΔT = t2 - t1 = 200°C - 400°C = -200°C

The negative sign indicates a decrease in temperature.

Substituting the values of m, c, and ΔT into the equation for Q:

Q = 390 kg * 500 J/(kg⋅°C) * (-200°C) = -39,000,000 J

Answer:

The amount of heat released is -39,000,000 Joules. To express the answer in Megajoules (MJ), we divide by 1,000,000:

Q = -39,000,000 J = -39 MJ

Therefore, the magnitude of the released heat is approximately -39 Megajoules (rounded to the nearest whole number).