Which statement about black holes is true?
A) Their event horizon is a physical surface boundary.
B) Their main-sequence mass was 5-10 solar masses.
C) They form from 1.4 solar mass stars.
D) Their escape velocity is greater than the speed of light.
E) They form an event horizon at twice the Schwartzschild radius.
D
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A mass hangs from a spring that is fixed to the ceiling. The mass is now pulled down and released so the mass oscillates up and down. Which of the following statements is true?
A. The gravitational force on the mass oscillates at the same frequency as the mass B. The kinetic energy of the oscillating mass is a constant C. Adding mass to the spring will make it oscillate faster D. The restoring force of the spring is equal to the weight of the mass E. None of these choices are true
An electron (m = 9.1 × 10^?31 kg) has a speed of 0.90 c. What is the difference between its relativistic momentum and its non-relativistic momentum (in kg m/s)?
a. 4.3 × 10^?22 b. 3.2 × 10^?22 c. 5.4 × 10^?22 d. 6.5 × 10^?22 e. 2.5 × 10^?22
When an artery gets a constricted region due to plaque, how does the pressure in this region compare to the pressure in an unconstricted region adjacent?
a. Since this is a closed system, the pressure is the same in both regions. b. In the constricted region the blood moves at a higher speed than in the unconstricted region resulting in an increased pressure. c. In the constricted region the blood moves at a higher speed than in the unconstricted region resulting in a decreased pressure. d. In the constricted region the blood moves at a lower speed than in the unconstricted region resulting in an increased pressure.
Two guitar strings are under the same tension and have the same length. If their fundamental frequencies are in a ratio of 3:2, what is the ratio of their masses?
A. 3/2 B. 2/3 C. 9/4 D. 4/9