The density of interstellar dust is very low, yet it still blocks starlight because
A) there is 100 times more opaque gas than dust present in the interstellar medium.
B) it is so cold it absorbs higher energy photons.
C) the dust particles are about the same size as the light waves they absorb.
D) the dust particles are irregular in shape.
E) ice particles reflect all light back toward their stars, not toward us.
C
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The open clusters were a population of relatively young stars, so where would you expect to see them from?
A.) In the halo with globular clusters. B.) In the disk. C.) In the bulge. D.) Only around the Sun. E.) Behind us.
Power: A typical incandescent light bulb consumes 75 W of power and has a mass of 30 g. You want to save electrical energy by dropping the bulb from a height great enough so that the kinetic energy of the bulb when it reaches the floor will be the same as the energy it took to keep the bulb on for 1.0 hour. From what height should you drop the bulb, assuming no air resistance and constant g?
Fill in the blank(s) with the appropriate word(s).
The work you do when pushing a shopping cart a given distance while applying twice as much force is
A) half as much. B) twice as much. C) four times as much. D) the same amount.
It is 6 km to Centerville, and you bicycle there in 20 minutes. Your speed is
A) 9 km/hr. B) 24 km/hr. C) 2 km/hr. D) 18 km/hr. E) 12 km/hr.