Good tracers of the spiral arms of our galaxy are all I. very old. II. very young. III. very luminous. IV. moving with large radial velocities
a. I & III
b. I & IV
c. II & III
d. II & IV
e. I, III, & IV
c
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The three lowest resonate frequencies of a system are 50 Hz, 150 Hz, and 250 Hz. The system could be
A. a tube of air closed at both ends. B. a tube of air open at one end. C. a tube of air open at both ends. D. a vibrating string with fixed ends.
An instrument is thrown upward with a speed of 15 m/s on the surface of planet X where the acceleration due to gravity is 2.5 m/s2 and there is no atmosphere. How long does it take for the instrument to return to where it was thrown?
A) 12 s B) 6.0 s C) 10 s D) 8.0 s
Motion of the plates of Earth's crust is thought to be due to
a. the solar wind. b. convection from the hot interior. c. tides in the oceans. d. friction between wind and the land surface. e. Earth's magnetic field.
A solid object is made of two materials, one material having density of 2 500 kg/m3 and the other having density of 6 500 kg/m3 . If the object contains equal masses of the materials, what is its average density?
a. 3 611 kg/m3 b. 4 500 kg/m3 c. 4 611 kg/m3 d. 9 000 kg/m3 e. more information is needed