On the scale of the cosmic calendar, in which the history of the universe is compressed into 1 year, when did the dinosaurs become extinct?
A) in late December
B) in late November
C) in late October
D) in late September
E) in late August
A) in late December
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A black sphere (2.5-cm in diameter) is placed in a large infrared heating oven whose walls are maintained at 370°C. The temperature of the air in the oven is 90°C and the heat-transfer coefficient for convection between the surface of the sphere and the air is 30 W/(m2 K). Estimate the net rate of heat flow to the sphere when its surface temperature is 35°C.
GIVEN
• A black sphere in a large infrared heating oven
• Sphere diameter (D) = 2.5 cm = 0.025 m
• Oven wall temperature (T2) = 370°C = 643 K
• Oven air temperature (T?) = 90°C = 363 K
• Convective heat transfer coefficient (hc) = 30 W/(m2 K)
• Sphere surface temperature (T1) = 35°C = 308 K
FIND
• The net rate of heat flow to the sphere (qtotal)
ASSUMPTIONS
• The oven walls are diffuse
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/m2K4
Earth's magnetic field is generated by the dynamo effect in the
a. molten metallic core. b. solid central core. c. plastic mantle. d. crust. e. aurora.
A 5,000 kg satellite is orbiting the Earth in a circular path. The height of the satellite above the surface of the Earth is 800 km. The velocity of the satellite is 
A. 7,460 m/s. B. 6,830 m/s. C. 6,430 m/s. D. 5,950 m/s. E. 5,350 m/s.
Our solar system contains more than 100 Kuiper Belt objects larger than 300 km in diameter
Indicate whether the statement is true or false