Physics Answers

A steady flow, steady state thermodynamic system receives 45 kg/min of a fluid at 207kPa

and discharges it from point 24 m. above the entrance section at 1034 kPa. The fluid

enters with a velocity of 36.6 m/s and leaves with a velocity of 12 m/s. During this process,

there are supplied 7 kW of heat from an external source, and the increase in enthalpy is

4.6 kJ/kg. Determine the work in kW and in horsepower.

Steam enters a turbine stage with an enthalpy of 3628 kJ/kg at 70 m/s and leaves at the

same stage with an enthalpy of 2846 kJ/kg at 124 m/s. Calculate the work per kg done by

the steam.

Steam with a flow rate of 1360 kg/h enters an adiabatic nozzle (adiabatic, Q=0) at 1378

kPa, specific volume of 0.147 m3

/kg, and specific internal energy of 2510 kJ/kg. The exit

conditions are 137.8 kPa, 1.099 m3

/kg specific volume, and 2263 kJ/kg of specific internal

energy. Find the exit velocity.

In a steady flow apparatus, 135 kJ of work is done by each kg. of fluid. The specific volume,

pressure, and velocity of the fluid at the inlet are: 0.37 m3

/kg, 600kPa, and 16 m/s. At the

outlet are: 0.62 m3

/kg, 100 kPa, and 270 m/s. The inlet is 32 m. above the discharge line.

The heat loss between the inlet and discharge is 9 kJ/kg. In flowing through this apparatus,

does the specific internal energy increases or decreases?

Air flows steadily at the rate of 0.5 kg/s through an air compressor, entering at 7 m/s, 100

kPa, 0.95 m3

/ kg specific volume, and leaving at 5 m/s, 700 kPa, and 0.19 m3

/kg specific

volume. The internal energy of the air leaving is 90kJ/kg greater than that of the air

entering. Cooling water in the compressor jackets absorb heat from the air at the rate of

58 kJ/s. Calculate the work.

An elevator in on the thirtieth floor of an office building when supporting cables shears.

The elevator drops vertically to the ground where several springs absorb the impact of the

elevator. The elevator mass is 2500 kg and it is 100 m. above the ground. Determine: a)

the potential energy of the elevator before its fall, b) the velocity and kinetic energy the

instant before the impact.

A closed system containing a gas expands slowly in a piston/cylinder from 600kPa and

0.1 m3

to a final volume of 0.5 m3

. Determine the work done if the pressure distribution

is determined to be: a) Pv = C, b) pV1.4 = C, c) P = C,

d) p = -300V + 630 kPa where V is in m3

Which of the following statements is true for a projectile launched at an angle of 45 with the horizontal?

Since the Christmas season is approaching, a shopping mall owner decides to decorate his mall with the decorative elements as shown in the following

circuit. The values of the resistances offered by different decorative stars are as follows: the resistance offered by red star is 8 ohms, blue star offers a

resistance of 6 ohms, while the pink star offers resistance of 5 ohms and the green star has a resistance of 10 ohms. The owner decides to simply his circuit,

in this regard, find the Thevenin's equivalent across the green star and also determine the current that will flow across the green star

A dielectric with a positive charge of 13 C has 18.75X10 ^18 electrons added to it. What is the net charge of the dielectric in coulombs ?