Galaxy A receding from Galaxy B at a velocity of 75000 km/s, from the perspective of Galaxy B. Hubble's Law says that V=H0 x D. About how far is Galaxy A from Galaxy B? Use a value of 75 km/s/Mpc for Hubble's constant.
A. 50000 Mpc
B. 100 Mpc
C. 500,000 Mpc
D. 5000 Mpc
E. 1000 Mpc
Ans: E. 1000 Mpc
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The high eccentricity of Mercury's orbit probably has nothing to do with Mercury's 3:2 synch of rotation and revolution
Indicate whether the statement is true or false
A spherical communications satellite 2-m in diameter is placed in orbit around the earth. The satellite generates 1000 W of internal power from a small nuclear generator. If the surface of the satellite has an emittance of 0.3 and is shaded from solar radiation by the earth, estimate the surface temperature. What is the temperature if the satellite with an absorptivity of 0.2 is in an orbit in which it is exposed to solar radiation? Assume the sun is a blackbody and irradiation striking the satellite is 1366 W/m2 and state your assumptions.
GIVEN
• Spherical satellite
• Diameter (D) = 2 m
• Heat generation = 1000 W
• Emittance (?) = 0.3
• Absorptivity of satellite (?)=0.2
• Solar irradiation(G)=1366 W/m2
FIND
• The surface temperature (Ts)
• Surface temperature of satellite
ASSUMPTIONS
• The satellite radiates to space which behaves as a blackbody enclosure at 0 K
• The system is in steady state
SKETCH
PROPERTIES AND CONSTANTS
The Stefan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)
How many nodes does a standing wave in a string have at the frequency of the sixth harmonic?
a. 12 c. 3 b. 6 d. The answer is not given.
Gamma rays have a small
A) wavelength. B) energy. C) frequency. D) mass.