Where does the celestial equator intersect the ecliptic?
A. at the zenith
B. at the southern horizon
C. at the summer solstice
D. at the equinoxes
at the equinoxes
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The refrigeration system for an indoor ice rink is to be sized by an HVAC contractor. The refrigeration system has a COP (coefficient of performance) of 0.5. The ice surface is estimated to be –2°C and the ambient air is 24°C. Determine the size of the refrigeration system in kW required for a 110 m diameter circular ice surface.
GIVEN
? Round ice rink
? Diameter (D) = 110 m
? Ice surface temperature (Ts) = – 2°C
? Air temperature (T?) = 24°C
? COP of refrigeration system = 0.5
FIND
? Size of the refrigeration system required
ASSUMPTIONS
? Air is quiescent
? The effects of sublimation are negligible
? Radiation heat transfer is negligible
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at the mean temperature of 11°C
A food calorie is a kilocalorie in SI units. What would be the speed of a 1000 kg car traveling such that its kinetic energy is equal to the energy contained in one 250-calorie jelly doughnut?
A. 46 m/s B. 65 m/s C. 32 m/s D. 22 m/s
The radio waves emitted from Sagittarius A* region take how long to travel to Earth?
A. 220 million years B. 50,000 years C. 100,000 years D. 8.5 years
Nuclear Binding Energy: A beryllium-8 nucleus at rest undergoes double alpha decay as follows:
The known atomic masses are:
What is the kinetic energy of each departing alpha particle? (1 u = 931.5 MeV/c2)
A. 46 keV B. 65 keV C. 92 keV D. 130 keV E. 180 keV