Chapter 1, Problem 1P

Problem 2 Consider the power drawn by a resistance load in a DC circuit. The power is calculated as P = VI or P = 1²R. It is given that the normalized uncertainty or % percentage uncertainty in measurements of I, R, and V are the same. Find the uncertainty in P using the two different expressions for power. Is the uncertainty using the two methods the same? If not, WHY, explain?

A piston–cylinder device contains 3 kg of nitrogen initially at 100 kPa and 25°C. Nitrogen is now compressed slowly in a polytropic process during which PV1.3 = constant until the volume is reduced by one-half. Determine the work done and the heat transfer for this process. The gas constant of N2 is R = 0.2968 kPa·m3/kg·K. The cv value of N2 at the anticipated average temperature of 350 K is 0.744 kJ/kg·K (Table A-2b).   The work done for this process is  kJ. The heat transfer for this process is  kJ.

I tried solving this one but I have no idea where I went wrong can you please help me out with this?

During a picnic on a hot summer day, all the cold drinks disappear quickly, and the only available drinks are those at the ambient temperature of 85°F. In an effort to cool a 12- fluid-oz drink in a can, a person grabs the can and starts shaking it in the iced water of the chest at 32°F. Using the properties of water for the drink, determine the mass of ice that will melt by the time the canned drink cools to 37°F. The density and specific heat of water at the average temperature of (85+37)/2 = 61ºF are ρ = 62.3 lbm/ft3 and cp = 1.0 Btu/lbmºF (Table A-3E). The heat of fusion of water is 143.5 Btu/lbm.   The mass of ice that will melt by the time the canned drink cools to 37°F is  lbm.

Steam enters a nozzle at 400°C and 800 kPa with a velocity of 10 m/s and leaves at 375°C and 400 kPa while losing heat at a rate of 26.5 kW. For an inlet area of 800 cm2, determine the velocity and the volume flow rate of the steam at the nozzle exit. Use steam tables.   At the left side of the lines, 800 kilo Pascal, 400 degree Centigrade, 10 meters per second are shown. At the right side of the lines, 400 kilo Pascal, 375 degree Centigrade are shown.   The velocity of the steam at the nozzle exit is  m/s.   The volume flow rate of the steam at the nozzle exit is  m3/s.

A saturated liquid–vapor mixture of water, called wet steam, in a steam line at 1450 kPa is throttled to 50 kPa and 100°C. What is the quality in the steam line? Use data from the steam tables.   Above the right side of the tube, 50 kilos 100 degree Centigrade indicated.   The quality in the steam line is  .

I tried this problems a couple of ways but I don't know what I'm doing wrong can you help me please?

Refrigerant-134a enters a compressor at 180 kPa as a saturated vapor with a flow rate of 0.35 m3/min and leaves at 900 kPa. The power supplied to the refrigerant during the compression process is 2.35 kW. What is the temperature of R-134a at the exit of the compressor?   The temperature of R-134a at the exit of the compressor is  °C.

Air enters the compressor of a gas-turbine plant at ambient conditions of 100 kPa and 25°C with a low velocity and exits at 1 MPa and 347°C with a velocity of 90 m/s. The compressor is cooled at a rate of 1500 kJ/min, and the power input to the compressor is 250 kW. Determine the mass flow rate of air through the compressor. The inlet and exit enthalpies of air are 298.2 kJ/kg and 628.07 kJ/kg.   The mass flow rate of air is  kg/s.