Asample consisting of 2 moles he is expanded isothermally at 0 degrees from 5.0dm3 to 20.0dm3. calculate w, q and deltau for each of the following situations: (i) a reversible expansion of the sample. (ii) an irreversible expansion of the sample against a constant external pressure equal to the final pressure of the gas. (iii) a free expansion (against zero external pressure i. e. in a vacuum) of the sample.

i)

ii)

ii)

Explanation:

As the initial and final states of the sample are the same, the ΔU of the sample is, for the three cases

since

i)Reversibly so can be calculated by  

and because of the first law of thermodynamics

ii)Irreversibly with

we can calculate by the law of ideal gases

then w can be calculated by

and  

iii)a free expansion so (there's no work at vaccum) and

8 m/s because for him to get the same amount of energy as ray is putting out, bobby, who weighs half as much as ray, needs to run twice as fast.

there is none because earth is stationary and flat.