- 1. Homework 1 Due 2/7/2014 Chapter 1 Problem: (1.45) If the water pressure at the base of the water tower shown below is 4.15 bar, determine the pressure of the air trapped above the water level, in bar. The density of the water is 103 kg/m3 and g is 9.81 m/s2 . True or False (1.60) b) Specific volume, the volume per unit mass, is an intensive property while volume and mass are extensive properties. d) If the value of any property of a system changes with time, that system cannot be at steady state (equilibrium). f) According to Archimedes’ principle, the magnitude of the buoyant force acting on a submerged body is equal to the weight of the body. (1.61) a) A refrigerant at an absolute pressure of 0.8 atm is at a gage pressure of 0.2 atm.
- 2. b) Temperature is the property that is the same for each of two systems when they are in thermal equilibrium. e) A control volume is a special type of closed system that does not interact in any way with its surroundings. Chapter 2 Problems: (2.2) An object whose mass is 400 kg is located at an elevation of 25 m above the surface of the earth. For g = 9.78 m/s2 , determine the gravitational potential energy of the object, in kJ, relative to the surface of the earth. (2.6) An object of mass 1000 kg, initially having a velocity of 100 m/s, decelerates to a final velocity of 20 m/s. What is the change in kinetic energy of the object, in kJ? (2.16) Beginning from rest, an object of mass 200 kg slides down a 10 m ramp. The ramp is inclined at an angle of 40° from the horizontal. If air resistance and friction between the object and the ramp are negligible, determine the velocity of the object, in m/s, at the bottom of the ramp. Let g = 9.81 m/s2 . (2.21) A major force opposing the motion of a vehicle is the rolling resistance of the tires, Fr, given by Fr = fw Where f is a constant called the rolling resistance coefficient and w is the vehicle weight. Determine the power, in kW, required to overcome rolling resistance for a truck weighing 322.5 kN that is moving at 110 km/h. Let f = 0.0069. (2.25) A gas in a piston-cylinder assembly undergoes a process for which the relationship for pressure and volume is pV2 = constant. The initial pressure is 1 bar, the initial volume is 0.1 m3 , and the final pressure is 9 bar. Determine a) the final volume, in m3 , and b) the work for the process, in kJ.
- 3. (2.31) Air contained within a piston-cylinder is slowly heated. As shown in figure p2.31, during the process the pressure first varies linearly with volume and then remains constant. Determine the total work, in kJ.