- #1
lwelch70
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Homework Statement
A closed system initially at rest on the surface of the Earth undergoes a process for which there is a net energy transfer to the system by work of 200 Btu. During the process, there is a net heat transfer from the system of 30 Btu. At the end of the process, the system has velocity of 200 ft/sec at an elevation of 200 ft. The mass of the system is 50lb and the local acceleration due to gravity is 32 ft/s2. Determine the change in internal energy of the system for this process, in Btu.
Homework Equations
[itex]\Delta[/itex]E = [itex]\Delta[/itex]U + [itex]\Delta[/itex]KE + [itex]\Delta[/itex] PE
The Attempt at a Solution
So I understand that the system initially has 200 Btu transferred to it. And 30 Btu taken away from the heat.
So my understanding of that is that [itex]\Delta[/itex]E is equal to 170 Btu. Correct?
In calculating the [itex]\Delta[/itex]KE, all I see is that initially it is 0, and after it is 1/2mv2. This gives my units in [itex]\frac{lbft^2}{s^2}[/itex]
How do I get this in Btu? I'm not very good with units.
Also, would I include [itex]\Delta[/itex]PE since the system is moving at the end of process?