Ancient astronomers often saw certain planets viewed, while viewed from Earth, slowly stop and then move westward, of which they called this movement _______________
Fill in the blank(s) with correct word
retrograde motion
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On the H-R diagram, 90 percent of all stars are ____
a. either giant or supergiant stars b. white dwarfs c. main sequence stars d. sred dwarfs e. binary stars
In general, the narrower the spectral line of a star:
A) the hotter the star is. B) the bigger the star is. C) the denser the star is. D) the smaller the star is. E) the cooler the star is.
One end of a copper rod is in thermal contact with a hot reservoir at T = 500 K and the other end is in thermal contact with a cooler reservoir at T = 300 K. Find the entropy change of each reservoir, and the total entropy change, when 8 000 J of heat energy are conducted from one end of the rod to the other with no change in the temperature distribution in the rod
As measured from the Earth, a spacecraft is moving at speed 0.80c toward a second spacecraft moving at speed 0.60c back toward the first spacecraft. What is the speed of the first spacecraft as viewed from the second spacecraft?
a. 0.81c c. 0.38c b. 0.95c d. 0.20c