What is the approximate surface temperature of a star with weak hydrogen absorption lines and strong absorption lines of ionized calcium?
A) 4,500 K B) 6,500 K C) 5,500 K D) 3,500 K
C
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Charge of a uniform density (8.0 nC/m2) is distributed over the entire xy plane. A charge of uniform density (3.0 nC/m2) is distributed over the parallel plane defined by z = 2.0 m. Determine the magnitude of the electric field for any point with z = 3.0 m
a. 0.79 kN/C b. 0.17 kN/C c. 0.62 kN/C d. 0.34 kN/C e. 0.28 kN/C
What observational evidence suggests that the centers of quasars are small, about a fraction of a light-year?
A. photographs of quasars B. the fact that quasars are so distant, and therefore are very young C. They emit radiation over a very wide range of wavelengths D. The intensity of their radiation fluctuates over periods of months E. All of these choices are correct.
The low density universe is an open one, with expansion continuing forever
Indicate whether the statement is true or false
For the astronauts inside an orbiting space vehicle the force of gravity that acts on them is
A) zero. B) mainly due to Earth below. C) mainly due to the mass of the space vehicle. D) mainly due to nearby planets and stars. E) none of the above