- #1
cardsrams82
- 5
- 0
Homework Statement
Given the specific heat of water is cw=4180 J/kgC
A 241 kg cast-iron engine contains water as a coolant. Suppose the engine's temperature is 31C when it is shut off and the air temperature is 15C. The heat given off by the engine and water in it as they cool to air temperature is 3.7X10^6 J. (Assume the specific heat of iron is 450 J/kgC)
What mass of water is used to cool the engine? Answer in units of kg.
Homework Equations
Q=mc(deltaT)
Qcold=-Qhot
The Attempt at a Solution
I first try using calorimetry to solve it by setting up an equation but ran into issues since I do not know the initial temperature of water. Any attempt at trying to substiute equations is giving me answers of 1, cancelling out the denominators and such. I then assumed that the combined heat given off (3.7X10^6J) was Q and tried to set the total Q = (MwCw(deltaT)). Again I keep running into the issue that I do not know the initial temperature of the water. I know the combined equilibreum temperate as the entire unit cools to the outside temperature of 15C. I know the heat exerted is 3.7X10^6. I know the mass of the material, the specific heat of both, and the initial temperature of the material. I assume the final heat is the same for both since both the engine and the water cooled to 15C as stated in the problem.What am I doing wrong and how should I go about solving this problem?