What are the rings of Saturn made of?
A. helium droplets
B. chunks composed of water, ice, and carbon compounds
C. small fragments of dust
D. a huge sheet of ice
Answer: B
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In the Bohr model of the hydrogen atom
a. energy is quantized. b. the electron's angular momentum is quantized. c. the emission spectrum is quantized. d. the absorption spectrum is quantized. e. all of the above
A distant palm tree on a hot dry day that often appears to be reflected from water is
A) due to light refracted upward as it grazes the hot surface. B) the inverse of a mirage. C) evidence that light travels in straight lines.
Ninety percent of all normal stars in a Hertzsprung-Russell (H-R) diagram are:
A) in the giant region. B) in the supergiant region. C) on the random sequence. D) on the main sequence.
A 250 g block is dropped onto a relaxed vertical spring that has a spring constant of k = 2.5 N/cm (Fig. 7-30 ). The block becomes attached to the spring and compresses the spring 12 cm before momentarily stopping. While the spring is being compressed, what work is done on the block by
(a) the gravitational force on it and
(b) the spring force?
(c) What is the speed of the block just before it hits the spring? (Assume that friction is negligible.)
(d) If the speed at impact is doubled, what is the maximum compression of the spring?