Compare the speed of spiral density waves with the orbital speeds of stars in the visible part of the Galactic disk
What will be an ideal response?
Spiral density waves move slower than the orbital speeds at the same distance from the center of a galaxy.
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A series circuit has a 50-Hz ac source, a 40-? resistor, a 0.70-H inductor, and a 60-?F capacitor, as shown in the figure. The rms current in the circuit is 1.6 A. What is the voltage amplitude of the source?
A. 390 V B. 330 V C. 270 V D. 220 V E. 190 V
Which of the following products of ratios gives the conversion factors to convert meters per second 
to miles per hour 
?
A.
B.
C.
D.
E.
What is the expected result from the merger of a large irregular and a small irregular galaxy?
What will be an ideal response?
Buoyancy: A 1.00-m3 object floats in water with 20.0% of its volume above the waterline. What does the object weigh out of the water? The density of water is 1000 kg/m3.
A. 1960 N B. 7840 N C. 9800 N D. 11,800 N