Problem 2.1 Given: A closed system consists of 0.5 kmole of ammonia occupying a

Question

Problem 2.1

Given: A closed system consists of 0.5 kmole of ammonia occupying a volume of 6 m3.

Find: The weight of the system (N) and the specific volume in m3/kmole and m3/kg.

Assume: Use g = 9.81 m/s2.

Problem 2.2

Given: Three kilogram of gas in a piston-cylinder assembly undergo a process during which the relationship between pressure and specific volume is PV0.5 = C, where C is a constant. The process starts with P1 = 250 kPa and V1 = 1.5 m3 and ends with P2 = 100 kPa.

Find: a) The final specific volume and b) plot the process, pressure (y-axis) versus volume (x-axis), for two intermediate pressures. Make a precise sketch of the process using uniform scaling.

Assume:

Analysis:

Problem 2.3

Given: An object whose weight is 100 lbf experiences a decrease in kinetic energy of 500 ft-lbf and an increase in potential energy of 1500 ft-lbf. The initial velocity and elevation of the object, each relative to the surface of the earth, are 40 ft/s and 30 ft.

Find: a) The final velocity (ft/s) and b) the final elevation (ft).

Assume: g = 32.17 ft/s2

Analysis:

Explanation / Answer

Answer 2.1 : Ammonia, molecular weight M = 17.03kg / kmol

n = 0.5 kmol ; m = 0.5 * 17.03 kg. = 8.515 kg.

Specific volume = 6 m3 / (0.5 x 17.03) =   0.7046 m3/ kg

                          or = 6 m3 / 0.5 = 12 m3 / kmol

Weight = m x g = 8.515 x 9.81 = 83.53 N

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