What direct evidence has been obtained for the existence of dark matter in galaxy clusters?
What will be an ideal response?
Gravitational lensing studies of a pair of colliding galaxy clusters show that the bulk of the matter is not located where the visible hot gas is found.
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Water flows over a waterfall 20. m high, at the rate of 4.0 × 104 kg/s. If this water powers an electric generator with a 40% efficiency, how many watts of electric power can be supplied?
What will be an ideal response?
The speed of Halley's comet, while traveling in its elliptical orbit around the sun,
A) decreases as it nears the sun. B) increases as it nears the sun. C) is zero at two points in the orbit. D) is zero at four points in the orbit. E) is constant.
A 30-?F capacitor is charged to 80 V and then connected across an initially uncharged capacitor of unknown capacitance C. If the final potential difference across the 30-?F capacitor is 20 V, determine C
a. 60 ?F b. 75 ?F c. 45 ?F d. 90 ?F e. 24 ?F
According to models of planetary interiors, the differences in mass among the four jovian planets (Jupiter, Saturn, Uranus, and Neptune) are due primarily to differences
A) in the amounts of material in the layers extending from the tops of their cores to their surfaces. B) in their core masses. C) in composition. D) in density.