The stellar parallax limit for ground-based telescopes is accurate for stars closer than ____
a. 10 parsecs
b. 50 parsecs
c. 100 parsecs
d. 200 parsecs
e. 500 parsecs
b
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Solar radiation at 600 W/m2 is absorbed by a black roof inclined at 30°C as shown. If the underside of the roof is well insulated, estimate the maximum roof temperature in Tinf= 20°C air.
GIVEN
• Inclined roof, well insulated on the underside
• Incline angle (?) = 30 degrees
• Air temperature = 20°C
• Solar radiation absorbed (qs) = 600 W/m2
FIND
• The maximum roof temperature
ASSUMPTIONS
• The roof behaves as a black body (? = 1.0)
• The sky behaves as a black body at 0 K
SKETCH
PROPERTIES AND CONSTANTS
The Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4).
Consider the situation shown below. Object A is a metal sphere with zero net charge, and objects B and C are particles with charges q and -q, respectively. Point P is at the sphere’s center. Answer each question below by choosing one of the arrows to the right of the picture or by choosing answer E. (If you are using the letters on the back cover to display your answer, you can indicate the double-letter choices by pointing to a letter with two fingers.) Which arrow best indicates the direction of the electric field at point P created by particle B?
A. A
B. B
C. C
D. D
E. Zero
F. AA
G. BB
H. CC
I. DD
Star formation ceased first in the:
A) nucleus. B) spiral arms. C) bulge. D) halo. E) galactic disk.
Avogadro's number is related to the universal gas constant R and the number of moles n by:
a. NA = Rn b. NA = R/n c. NA = n/R d. Avogadro's number cannot be related to these two quantities alone.