Galileo's telescopic discoveries of mountains on the Moon and spots on the Sun were controversial because they suggested that the Sun and Moon
a. were the same kind of object.
b. were not perfect spheres.
c. were inhabited.
d. orbited each other.
e. did not orbit Earth.
b
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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
Ptolemy was important in the history of astronomy because he
A) developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries. B) developed the first scientific model of the universe. C) was the first to create a model of the solar system that placed the Sun rather than the Earth at the center. D) was the first to believe that all orbits are perfect circles.
Our Sun will first become a red giant, then a white dwarf, and finally a brown dwarf
Indicate whether the statement is true or false
As long as an object is not gaining or losing mass, a net force on the object will cause a change in
A) acceleration. B) direction. C) weight. D) speed. E) velocity.