ME 200 – Fall 2015
Homework#1
Due Friday, September 4, 2015
Problem 1:
A 2 m3 closed, rigid tank contains air at 25C and 1 bar pressure. The mass of air in the
tank is 2.5 kg.
List numerical values of four intensive and two extensive properties.
Answers: Not attached
Problem 2:
A thermodynamics professor insists that students should use correct units. On a
particular quiz, however, students who did the problem correctly arrived at the same
numerical value of temperature irrespective of using F or C units.
(a) What was the numerical value of the temperature (F and C)?
(b) Determine the corresponding absolute temperature (K and R).
Answers: Not attached
Problem 3:
A 10 m3 rigid tank has two sections separated by a membrane. Each section contains
nitrogen gas. The nitrogen gas in section A has an initial density of 1.6 kg/m3 and the
nitrogen gas in section B has a mass of 6 kg. At a certain time, the membrane is
punctured. The final density of the nitrogen gas in the tank is found to be 1.8 kg/m3.
Determine the initial density (kg/m3) of nitrogen gas that existed in section B.
Answer: 2.4 kg/m3
Problem 4:
A small experimental rocket (mass = 70 kg) is accelerated at the rate of 6 m/s2. Neglect
any frictional effects and assume that the local gravitational constant is 9.45 m/s2.
(a) Determine the force required when the rocket is moving horizontally. Express the
answer in N and lbf.
(b) What is the force required when the rocket is moving vertically upwards? Express the
answer in N and lbf.
Answers: (a) 420 N, 94.1 lbf; (b) 1081.5 N, 242.3 lbf
Problem 5:
A diver is snorkeling 10 feet under water in coral reefs off the east coast of Florida. At
this location, the density of water is 62 lbm/ft3, the atmospheric pressure is 14.7 psia, and
local acceleration due to gravity is 32 ft/s2.
Which of the following is (are) the correct pressure on the ear drums of the driver?
616.65 lbf/ft2 (absolute)
616.65 lbf/ft2 (gauge)
4.28 psia
4.28 psig
18.98 psia
18.98 psig
Answers: Not attached
Problem 6:
Fresh water and sea water flowing in parallel horizontal pipelines are connected to each
other by a double U-tube manometer, as shown below. Assume that the density of fresh
water is 996 kg/m3, density of sea water is 1035 kg/m3, density of mercury is 13,529
kg/m3, and density of air is 1.2 kg/m3.
(a) Determine the pressure difference (kPa) between the two pipelines.
(b) Can the air column be ignored in your analysis?
(c) If the air is replaced with oil of specific gravity 0.72, then what is the pressure
difference (kPa) between the two pipelines? Can the oil column be neglected?
Answers: (a) 3.36 kPa; (b) Not attached; (c) 8.28 kPa, Not attached