When we see a half Moon in the sky, the lines between Earth, Moon, and Sun
A) are equal in length.
B) are parallel to one another.
C) form a right triangle.
D) all of the above
Answer: C
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Compute the average emittance of anodized aluminum at 100°C and 650°C from the spectral curve. Assume ?? = 0.8 for ? > 9 ?m
GIVEN
The spectral curve for anodized aluminum
FIND
The average emittance (?) at (a) 100°C = 373 K, and, (b) 650°C = 923 K
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 10–8 W/(m2 K4)
Your mass is 50 kg. Suppose you are standing on a scale in an elevator that is approaching a top floor and decreasing its speed at the rate of 3 m/s every second. What would be the reading on the scale?
A. 0 N B. 150 N C. 740 N D. 640 N E. 340 N
If the mass of a body were doubled, its gravity would become 4 times stronger
Indicate whether the statement is true or false
Many disk galaxies, such as Andromeda and the Milky Way, are thought to have extended halos of dark matter because the disk circular orbital speed is observed to ____________ increasing distances from the disk center
a. stay constant with b. decrease with c. be totally absent at