Galactic disks appear blue because:
A) they contain no G, K, or M dwarfs.
B) they contain only blue reflection nebulae.
C) dust obscures the longer, red, wavelengths.
D) O and B blue giants are much brighter than G, K, or M dwarfs.
E) dark matter gravitationally shifts all wavelengths towards the blue.
D
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A model rocket sits on the launch pad until its fuel is ignited, blasting the rocket upward. During the short time of blast-off, as the ignited fuel goes down, the rocket goes up because:
a. the fuel pushes on the ground. b. air friction pushes on the escaping fuel. c. the downward force of gravity on the rocket is less than the rate of downward momentum increase of the fuel. d. of none of the above reasons.
A block of metal weighs 40 N in air and 30 N in water. What is the buoyant force on the block due to the water? The density of water is 1000 kg/m3
A) 10 N B) 30 N C) 40 N D) 70 N
A lunar month is about 28 days. If the Moon were farther from Earth than it is now, the lunar month would be
A) more than 28 days. B) less than 28 days. C) about 28 days.
The figure below shows a single lens with two rays of white light incident on it from the left. Sketch the paths of the blue, yellow, and red components of each of these rays to the point where the light from the upper and lower rays would meet
?
What will be an ideal response?