A hole is punched in a full milk carton, 10 cm below the top. What is the initial velocity of outflow?
a. 1.4 m/s
b. 2.0 m/s
c. 2.8 m/s
d. 3.9 m/s
e. 4.2 m/s
a
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Due to their great masses, all four jovian worlds are much denser than the Earth
Indicate whether the statement is true or false
Uncertainty Principle Using Momentum and Position: You measure the velocity of an electron to an accuracy of ±22.6 m/s. What is the minimum uncertainty in its position? (h = 6.626 × 10-34 J ? s, melectron = 9.11 × 10-31 kg)
A. 8.05 ?m B. 4.03 ?m C. 16.1 ?m D. 32.2 ?m E. 5.12 µm
The surfaces of two concentric spheres having radii of 75 and 100 mm are maintained at 325 K and 275 K, respectively.
(a) If the space between the spheres is filled with nitrogen at 500 kPa, estimate the
convection heat transfer rate.
(b) If both sphere surfaces are black, estimate the total rate of heat transfer between them.
(c) Suggest ways to reduce the heat transfer.
GIVEN
? Concentric spheres with nitrogen between them
? Nitrogen pressure (p) = 500 kPa
? Sphere radii
? Inner sphere (ri) = 75 mm = 0.075 m
? Outer sphere (ro) = 100 mm = 0.1 m
? Sphere temperatures
? Inner sphere (Ti) = 325 K
? Outer sphere (To) = 275 K
? Both spheres are black
FIND
(a) Convective heat transfer (qc)
(b) Total heat transfer (qtotal)
(c) Suggest ways to reduce the heat transfer
ASSUMPTIONS
? Sphere temperatures are constant and uniform
? Only the density of the nitrogen is affected significantly by pressure
? The nitrogen behaves as an ideal gas
PROPERTIES AND CONSTANTS
From Appendix 2, Table 33, for Nitrogen at atmospheric pressure and the mean temperature of 300 K
The density of the nitrogen at 500 kPa can be calculated from the ideal gas law
In 1991, a utility owned a nuclear plant that was online 95% of the year, the oil burning plant was only out for unscheduled maintenance on the air pollution system 15% of the time, and the gas-fired turbines were online 15% of the time
The nuclear plant is rated at 1000 MW, the oil plant at 940 MW, and the turbine at 200 MW. (See Fig. 8.15.) a. What is the total cost of running these three plants for the utility? b. How much would the utility have to charge per kWh to make a profit?