Get it Right today, for today will never come again Prepared by: Seyi Ayoola Engr. Richelle Mae D. Mendoza

PROBLEM SET #1: BASIC THERMODYNAMICS

1. Separate the list Pressure, Force, Volume, specific volume v, density , temperature T, acceleration a, mass m, length L, time t and velocity V into intensive, extensive and non-properties.

2. A tank has two rooms separated by a membrane. Room A has 1 kg air and volume 0.5 m3, room B has 0.75 m3 air with density 0.8 kg/m3. The membrane is broken and the air comes to a uniform state. Find the final density of the air.

3. The reading on a mercury manometer at 70F (open to the atmosphere at one end) is 25.62 (in). The local acceleration due to gravity is 32.243 (ft)(s)-2. Atmospheric pressure is 29.86 (in Hg). What is the absolute pressure in (psia) being measured? The density of mercury at 70F is 13.543 g cm-3.

4. A steel plate of 950 kg accelerates from rest with 3 m/s2 for a period of 10s. What force is needed and

what is the final velocity?

5. A gas is confined in a 1.25(ft)-diameter cylinder by a piston, on which rests a weight. The mass of the piston and weight together is 250 (lbm). The local gravitational accelerationis 32.169 (ft)(s)-2, and the atmospheric pressure is 30.12 (inHg). (a) What is the force in (lbf) exerted on the gas by te atmosphere, the piston, and the weight,

assuming no friction between the cylinder and piston? (b) What is the pressure of the gas in (psia)? (c) If the gas in the cylinder is heated, it expands, pushing the piston and weight upward. If the

piston and weight are raised 1.7 (ft), what is the work done by the gas in (lbf ft)? What is the change in potential energy of the piston and weight?

6. The density of mercury changes approximately linearly with temperature as

Hg = 13595 2.5 T kg/ m3 T in Celsius so the same pressure difference will result in a manometer reading that is influenced by temperature. If a pressure difference of 100 kPa is measured in the summer at 35C and in the winter at 15C, what is the difference in column height between the two measurements?

7. A 5-kg piston in a cylinder with diameter of 100 mm is loaded with a linear spring and the outside atmospheric pressure of 100 kPa. The spring exerts no force on the piston when it is at the bottom of the cylinder and for the state shown, the pressure is 400 kPa with volume 0.4 L. The valve is opened to let some air in, causing the piston to rise 2 cm. Find the new pressure.

8. Two piston/cylinder arrangements, A and B, have their gas chambers connected by a pipe. Cross-sectional areas are AA = 75 cm2 and AB = 25 cm2 with the piston mass in A being mA = 25 kg. Outside pressure is 100 kPa and standard gravitation. Find the mass mB so that none of the pistons have to rest on the bottom.

9. When you move up from the surface of the earth the gravitation is reduced as g = 9.807 3.32 10-6

z, with z as the elevation in meters. How many percent is the weight of an airplane reduced when it cruises at 11 000 m?

10. A 2.5 m tall steel cylinder has a cross sectional area of 1.5 m2. At the bottom with a height of 0.5 m is liquid water on top of which is a 1 m high layer of gasoline. The gasoline surface is exposed to atmospheric air at 101 kPa. What is the highest pressure in the water?

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