Which of the following observations provides direct evidence that galaxies containing active galactic nuclei have central, supermassive black holes?
A) the high orbital velocities of stars and gas clouds at the very centers of these galaxies
B) jet velocities that approach the speed of light observed in gas at great distances from the galaxy centers
C) large quantities of high-energy emission such as x-rays and gamma rays coming from these galaxies
D) huge dark regions in the centers of these galaxies
A) the high orbital velocities of stars and gas clouds at the very centers of these galaxies
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A 50.0-kg block is being pulled up a 15.0° slope by a force of 300 N which is directed 30.0° above the slope. The coefficient of kinetic friction between the block and the slope is 0.200. What is the acceleration of the block?
A) 1.36 m/s2 B) 0.158 m/s2 C) 0.924 m/s2 D) 0.520 m/s2 E) 1.47 m/s2
Light of wavelength 439 nm is incident on a metallic surface with a resultant photoelectric stopping potential of 1.2 V. What is the work function of the metal? (h = 6.63 × 10^?34 J?s, c = 3.00 × 10^8 m/s, 1 eV = 1.60 × 10^?19 J, and 1 nm = 10?9 m)
a. 1.63 eV b. 2.83 eV c. 4.03 eV d. 0.82 eV e. 2.02 eV
What is the minimum speed needed by a ground-state hydrogen atom for its kinetic energy to be enough to ionize the atom in a collision? (1 eV = 1.60 × 10-19 J, mH ? mproton = 1.67 × 10-27 kg)
A) 66.5 km/s B) 51.0 km/s C) 21.7 km/s D) 113 km/s E) 44.2 km/s
An object is placed 6.0 cm in front of a convex mirror with a radius of curvature of 16.0 cm. Which of the following statements describes the image?
A) The image is upright and 3.4 cm in front of the mirror. B) The image is inverted and 3.4 cm behind the mirror. C) The image is upright and 3.4 cm behind the mirror. D) The image is inverted and 3.4 cm in front of the mirror. E) none of the above