CANKAYA UNIVERSITY

FACULTY OF ENGINEERING AND ARCHITECTURE

MECHANICAL ENGINEERING DEPARTMENT

ME 211 THERMODYNAMICS I

FALL 2015

HW # 1 SOLUTIONS

1) A 1500-kg car moving at 20 km/h is accelerated at a constant rate of 4 m/s2 up to a

speed of 75 km/h. What are the force and total time required?

2) A stainless steel storage tank contains 5 kg of oxygen gas and 7 kg of nitrogen gas.

How many kmoles are in the tank?

3) A tank has two rooms separated by a membrane. Room A has 1.5 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.

4) One kilogram of diatomic oxygen (O2 molecular weight 32) is contained in a 500- L tank.

Find the specific volume on both a mass and mole basis (v and ). v.

5) A valve in a cylinder shown in figure has a cross sectional area of 11 cm2 with a

pressure of 735 kPa inside the cylinder and 99 kPa outside. How large a force is needed

to open the valve?

6) A piston/cylinder with cross sectional area of 0.01 m2 has a piston mass of 100 kg resting on

the stops, as shown in figure. With an outside atmospheric pressure of 100 kPa, what should the

water pressure be to lift the piston?

7) A probe is lowered 16 m into a lake. Find the absolute pressure there.

8) Blue manometer fluid of density 925 kg/m3 shows a column height difference of 3 cm

vacuum with one end attached to a pipe and the other open to p0 = 101 kPa atmospheric

pressure. What is the absolute pressure in the pipe?

9) The pressure gauge on an air tank shows 50 kPa when the diver is 10 m down in the

ocean. At what depth will the gauge pressure be zero? What does that mean?

10) A vacuum gage connected to a chamber reads 35 kPa at a location where the atmospheric

pressure is 92 kPa. Determine the absolute pressure in the chamber.

Solution

11) The absolute pressure in a tank is 115 kPa and the local ambient absolute pressure is 97

kPa. If a U-tube with mercury (density = 13 550 kg/m3) is attached to the tank to measure

the gauge pressure, what column height difference will it show?

12) The absolute pressure in water at a depth of 9 m is read to be 185 kPa. Determine (a) the

local atmospheric pressure, and (b) the absolute pressure at a depth of 5 m in a liquid

whose specific gravity is 0.85 at the same location.

13) A gas is contained in a vertical, frictionless piston–cylinder device. The piston has a mass

of 3.2 kg and a cross sectional area of 35 cm2. A compressed spring above the piston

exerts a force of 150 N on the piston. If the atmospheric pressure is 95 kPa, determine the

pressure inside the cylinder.

14) Both a gage and a manometer are attached to a gas tank to measure its pressure. If the

reading on the pressure gage is 80 kPa, determine the distance between the two fluid

levels of the manometer if the fluid is (a) mercury (𝜌 = 13 600 𝑘𝑔/𝑚3 ) or (b) water (𝜌=

1000 kg/𝑚3).