On a graph of luminosity versus color for galaxies, shown below, many galaxies form a clump known as the "blue cloud." Why are galaxies in the blue cloud blue?
A) They contain hot, young stars that indicate active star formation.
B) They are moving slower than galaxies in the red cloud.
C) They contain lots of dust that cause the bluish color.
D) They contain cold, dying stars that are fading to black.
E) They are all moving toward us, causing them to be blueshifted.
A) They contain hot, young stars that indicate active star formation.
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The shortest wavelength of visible light is approximately 400 nm. Express this wavelength in centimeters
A) 4 × 10-5 cm B) 4 × 10-7 cm C) 4 × 10-9 cm D) 4 × 10-11 cm E) 400 × 10-11 cm
The "energy efficiency" of a device is
A) the total energy put into the device divided by its useful energy output. B) its thermal energy output divided by the total energy put into the device. C) its total energy output divided by the total energy put into the device. D) its useful energy output divided by the total energy put into the device. E) the total energy put into the device divided by its thermal energy output.
A person runs up a long flight of stairs in 10 seconds. If the person's weight is 600 N and the vertical height of the stairs is 20 meters, the person's power output is __________
Fill in the blank(s) with correct word
A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in thermal contact
The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium? A) the copper B) the aluminum C) neither; both experience the same size temperature change D) it is impossible to tell without knowing the masses E) it is impossible to tell without knowing the volumes