Many galaxies with erupting black holes are found ____
a. in poor clusters with little intergalactic gas
b. isolated in space
c. in one of a pair of orbiting galaxies
d. very close to the Milky Way galaxy
e. in the Local Group
c
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Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?
A) There would be a large empty region in our solar system between the orbit of Mars and the Kuiper belt. B) Earth would orbit much closer to the Sun. C) Neither the asteroid belt nor Oort cloud would exist. D) Earth would have suffered far fewer impacts.
Hydrogen has absorption lines at 656 nm and 486 nm. Where are the emission lines from hydrogen in this part of the electromagnetic spectrum?
A. 656 nm and 486 nm B. 826 nm and 656 nm C. 571 nm and 401 nm D. 486 nm and 316 nm
How small a time interval is needed for a good calculation of instantaneous speed?
a. Instantaneous speed is calculated for a single instant. b. Three days is small enough. c. Use the longest interval of travel to avoid numerical error. d. An interval short enough so that the answer won't change very much if you use a shorter one. e. A single second is short enough.
When a positive charge q is placed in the field created by two other charges Q1 and Q2, each a distance r away from q, the acceleration of q is
a. in the direction of the charge Q1 or Q2 of smaller magnitude. b. in the direction of the charge Q1 or Q2 of greater magnitude. c. in the direction of the negative charge if Q1 and Q2 are of opposite sign. d. in the direction of the positive charge if Q1 and Q2 are of opposite sign. e. in a direction determined by the vector sum of the electric fields of Q1 and Q2.