Molecular Physics | Thermodynamics Answers

Steam enters a turbine 80 lb_m of steam per minute with an enthalpy of 1700 Btu/lb and velocity of 98 ft/s. It leaves the turbine at 1400 Btu/lb at 880 ft/s. The heat loss is 90,000 Btu/hr. Find the horsepower output of turbine. 

W = ____ HP

Answer in 2 decimal places

The flow energy of 142 liters/min of a fluid passing a boundary to a system is 108.5 kJ/min. Determine the pressure at this point. 

p = ___ kPa

Answer in 2 decimal places

Work is done by a substance in a reversible nonflow manner in accordance with v = (700/p) m³, where p is in kPaa. Evaluate the work done on or by the substance as the pressure increases from 70 kPaa to 700 kPaa. 

W = kJ

Answer in 2 Decimals

A 2000-kg elevator accelerates upward uniformly at 1 m/s² from a stopped position. (a) What is the tension in the lifting cable in kN? (b) At the end of 4 s of operation, what will be the kinetic energy and the change of potential energy in kJ? Local gravity acceleration is 9.70 m/s²

T =

KE = PE =

The following is the equation which connects u, p and v for several gases

u = a + bpv

where a and b are constants. Prove that for a reversible adiabatic process,

pv^γ = constant, where γ = b +1/b

A fluid is contained in a cylinder by a spring-loaded, frictionless piston

so that the pressure in the fluid is a linear function of the volume (p = a + bV). The internal energy

of the fluid is given by the following equation

U = 42 + 3.6 pV

where U is in kJ, p in kPa, and V in cubic metre. If the fluid changes from an initial state of

190 kPa, 0.035 m3 to a final state of 420 kPa, 0.07 m3, with no work other than that done on the

piston, find the direction and magnitude of the work and heat transfer.

Define phase. What is meant by phase angle? Draw a graph and derive it as well.

. The following equation gives the internal energy of a certain substance

u = 3.64 pv + 90

where u is kJ/kg, p is in kPa and v is in m3/kg.

A system composed of 3.5 kg of this substance expands from an initial pressure of 500 kPa

and a volume of 0.25 m3 to a final pressure 100 kPa in a process in which pressure and volume are

related by pv1.25 = constant.

(i) If the expansion is quasi-static, find Q, ∆U and W for the process.

(ii) In another process, the same system expands according to the same pressure-volume

relationship as in part (i), and from the same initial state to the same final state as in part (i), but

the heat transfer in this case is 32 kJ. Find the work transfer for this process.

(iii) Explain the difference in work transfer in parts (i) and (ii).

A stone of 20 kg mass and a tank containing 200 kg water comprise a

system. The stone is 15 m above the water level initially. The stone and water are at the same

temperature initially. If the stone falls into water, then determine ∆U, ∆PE, ∆KE, Q and W, when

(i) the stone is about to enter the water,

(ii) the stone has come to rest in the tank, and

(iii) the heat is transferred to the surroundings in such an amount that the stone and water

come to their initial temperature.

. A quantity of steam at 10 bar and 0.85 dryness occupies 0.15 m3. Determine the heat supplied to raise the temperature of the steam to 300°C at constant pressure and

percentage of this heat which appears as external work.

Take specific heat of superheated steam as 2.2 kJ/kg K.