The masses of stars are found by measurements of
A) light intensity.
B) temperature.
C) Doppler shifting.
D) binaries.
E) relative sizes.
Answer: D
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Which of the following words best describes the sum total of all matter and energy that exists?
A) supercluster B) universe C) multiverse D) macrocosm
Compared to a sound of 40 decibels, the intensity of a sound of 50 decibels is
A) 10 times as much. B) 100 times as much. C) 1000 times as much. D) 10,000 times as much. E) more than 10,000 times as much.
An alpha particle is a nucleus of helium. It has twice the charge and four times the mass of the proton
When they were very far away from each other, but headed toward directly each other, a proton and an alpha particle each had an initial speed of 0.0030c, where c is the speed of light. What is their distance of closest approach? Hint: There are two conserved quantities. Make use of both of them. (c = 3.00 × 108 m/s, k = 1/4??0 = 8.99 × 109 N ? m2/C2, e = 1.60 × 10-19 C, mproton = 1.67 × 10-27 kg) A) 2.1 × 10-13 m B) 3.3 × 10-13 m C) 2.6 × 10-13 m D) 2.9 × 10-13 m
A car enters a level, unbanked semi-circular hairpin turn of 100-m radius at a speed of 28 m/s. The coefficient of friction between the tires and the road is ? = 0.800 . If the car maintains a constant speed of 28 m/s, it will
a. attempt to dig into the road surface. b. tend to veer toward the center of the semicircle. c. arrive safely at the end of the semicircle. d. tend to veer toward the outside of the circle. e. veer toward the center for the first quarter-circle, then veer toward the outside for the second quarter-circle.