речовину яка має меншу температуру плавлення (ОЛОВО ,наприклад)
80/x + 70/x =2
150/x=2
x=75
Расстояние между пунктами а и б равно 75км.
Единица измерения скорости в СИ - м/с, времени - с, расстояния - м
120 км/ч = 33,33 м/с
15 мин = 900 с
S = U*t
S=33,33 * 900 = 29997 м
_____________
Если нужно в км/ч:
15 мин=0,25ч
S=0,25*120=30 км
Дано: V = 2 * 10⁻² м³, m = 5 кг, t₁ = 10 °C, t₂ = 50 °C, η = 0.8
Найти: Q - ?
Решение:
Без потерь тепла:
![Q = Q_{1} + Q_{2} \ ; \ Q_{1} = c_{1}m_{1}\Delta t \ ; \ Q_{2} = c_{2}m\Delta t \\ \\ m_{1} = \rho V \ \rightarrow \ Q_{1} = c_{1} \rho V \Delta t \\ \\ Q = c_{1} \rho V \Delta t + c_{2}m\Delta t = \Delta t(c_{1}\rho V + c_{2}m) \\ \\ Q = 40(4200*1000*2*10^{-2} + 460*5) = 3452000 \ [Ds]](https://tex.z-dn.net/?f=+Q+%3D+Q_%7B1%7D+%2B+Q_%7B2%7D+%5C+%3B+%5C+Q_%7B1%7D+%3D+c_%7B1%7Dm_%7B1%7D%5CDelta+t+%5C+%3B+%5C+Q_%7B2%7D+%3D+c_%7B2%7Dm%5CDelta+t+%5C%5C+%5C%5C+m_%7B1%7D+%3D+%5Crho+V+%5C+%5Crightarrow+%5C+Q_%7B1%7D+%3D+c_%7B1%7D+%5Crho+V+%5CDelta+t+%5C%5C+%5C%5C+Q+%3D+c_%7B1%7D+%5Crho+V+%5CDelta+t+%2B+c_%7B2%7Dm%5CDelta+t+%3D+%5CDelta+t%28c_%7B1%7D%5Crho+V+%2B+c_%7B2%7Dm%29+%5C%5C+%5C%5C+Q+%3D+40%284200%2A1000%2A2%2A10%5E%7B-2%7D+%2B+460%2A5%29+%3D+3452000+%5C+%5BDs%5D+)
Ответ: Q = 3452 кДж
С потерями тепла:
![Q_{0} = Q_{1} + Q_{2} \ ; \ Q_{1} = c_{1}m_{1}\Delta t \ ; \ Q_{2} = c_{2}m\Delta t \\ \\ m_{1} = \rho V \ \rightarrow \ Q_{1} = c_{1} \rho V \Delta t \\ \\ Q_{0} = c_{1} \rho V \Delta t + c_{2}m\Delta t = \Delta t(c_{1}\rho V + c_{2}m) \\ \\ Q_{0} = 40(4200*1000*2*10^{-2} + 460*5) = 3452000 \ [Ds] \\ \\ Q = \dfrac{Q_{0}}{\eta} = \dfrac{3452000}{0.8} = 4315000 \ [Ds]](https://tex.z-dn.net/?f=+Q_%7B0%7D+%3D+Q_%7B1%7D+%2B+Q_%7B2%7D+%5C+%3B+%5C+Q_%7B1%7D+%3D+c_%7B1%7Dm_%7B1%7D%5CDelta+t+%5C+%3B+%5C+Q_%7B2%7D+%3D+c_%7B2%7Dm%5CDelta+t+%5C%5C+%5C%5C+m_%7B1%7D+%3D+%5Crho+V+%5C+%5Crightarrow+%5C+Q_%7B1%7D+%3D+c_%7B1%7D+%5Crho+V+%5CDelta+t+%5C%5C+%5C%5C+Q_%7B0%7D+%3D+c_%7B1%7D+%5Crho+V+%5CDelta+t+%2B+c_%7B2%7Dm%5CDelta+t+%3D+%5CDelta+t%28c_%7B1%7D%5Crho+V+%2B+c_%7B2%7Dm%29+%5C%5C+%5C%5C+Q_%7B0%7D+%3D+40%284200%2A1000%2A2%2A10%5E%7B-2%7D+%2B+460%2A5%29+%3D+3452000+%5C+%5BDs%5D+%5C%5C+%5C%5C+Q+%3D+%5Cdfrac%7BQ_%7B0%7D%7D%7B%5Ceta%7D+%3D+%5Cdfrac%7B3452000%7D%7B0.8%7D+%3D+4315000+%5C+%5BDs%5D++)
Ответ: Q = 4315000 Дж