How did Harlow Shapley use the period-luminosity relationship of RR Lyrae variables to determine the size of the Milky Way galaxy?
a. He determined the proper motion of globular clusters in the outer disk of the galaxy.
b. He found the distances to individual variables free floating in the halo.
c. He found the distances to open clusters found throughout the disk of the galaxy.
d. He found the distances to globular clusters distributed about the center of the galaxy.
D
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If an object moves with constant velocity,
a. its speed is constant. b. its direction is constant. c. its average speed is constant. d. its distance traveled per unit time is constant. e. all of these
A conducting rectangular loop of mass M, resistance R, and dimensions a × b is allowed to fall from rest through a uniform magnetic field which is perpendicular to the plane of the loop. The loop accelerates until it reaches a terminal speed (before the upper end enters the magnetic field). If a = 2.0 m, B = 6.0 T, R = 40 ?, and
M = 0.60 kg, what is the terminal speed?
a.
1.6 m/s
b.
20 m/s
c.
2.2 m/s
d.
26 m/s
e.
5.3 m/s
Two stereo speakers mounted 4.52 m apart on a wall emit identical sound waves. You are standing at the opposite wall of the room at a point directly between the two speakers
You walk 2.11 m parallel to the wall, to a location where you first notice that the sound intensity is essentially zero. If the wall along which you are walking is from the wall with the speakers, what is the wavelength of the sound waves? The walls are cushioned to absorb sound reflections. A) 2.05 m B) 2.57 m C) 2.91 m D) 1.71 m
X-Ray Diffraction: Certain planes of a crystal of halite have a spacing of 0.399 nm. The crystal is irradiated by a beam of x-rays. First order constructive interference occurs when the beam makes an angle of 20° with the planes of the crystal surface. What angle does the beam make with the crystal planes for second order constructive?
A. 37° B. 40° C. 43° D. 46° E. 49°