![]() ![]() If you think about classical mechanics, for example, a ball heading towards the earth, (neglecting air resistance and approximating the distance near the surface of the earth), the force is F=N=kg(m/s^2). This tells you how fast the pressure is changing with volume for every kg of gas/atoms in the system per volume. Slope m, is equal to Pressure/Volume, or dimensionally: m=(F/A)/V in SI units, it will be kg/(m^5) or kg*(m^-4) s^(-2). The slope tells you how fast the pressure is changing with respect to volume. But in the either case, the magnitude of the work is still the area inside the PV cycle. if the cycle is counterclockwise, that means the higher line (higher W area) was R to L (negative work), so the total W is negative (work was done ON the gas). The difference between the two areas is, by definition, the area within the cycle and that is the work done BY the gas during the cycle.Īs for the sign, if the cycle is clockwise, that means the higher line (higher work area) was L to R (positive work), so the total W is positive. The total work of the cycle is the sum of these two works (areas under the curves), but since one is negative, it's essentially the difference. ![]() While the cycle is moving R to L (decreasing volume) the work done BY the gas is considered negative. ![]() While the cycle is moving L to R (increasing volume) the work done BY the gas (area under the curve) is considered positive. This is now explained in a little pop-up box in the middle of the article, but you may have missed it or it may have been added after your question. ![]()
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