When a star's inward gravity and outward pressure are balanced, the star is said to be
A) in hydrostatic equilibrium.
B) in gravitational collapse.
C) a stage 2 protostar.
D) in thermal expansion.
E) in rotational equilibrium.
A
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The increase in specimen strength with plastic strain is _____________ hardening.
Fill in the blank(s) with the appropriate word(s).
Most terrestrial planets have portions of their surface that appear to be significantly older than other portions of their surface. What evidence suggests that the surface of Venus is all of the same age?
a. Photos taken by probes that landed on Venus showed that all of the rocks were of the same age. b. The craters on Venus are randomly distributed in size and number across the surface. c. The volcanoes on Venus are not found in isolated groups, but are scattered around the planet. d. a and b e. all of the above
A very long string is tied to a rigid wall at one end while the other end is attached to a simple harmonic oscillator. Which of the following can be changed by changing the frequency of the oscillator?
A. The speed of the waves traveling along the string. B. The tension in the string. C. The wavelength of the waves on the string. D. All of the above. E. None of the above.
Why was the discovery of a substantial magnetic field around Mercury a surprise? How was it detected?
What will be an ideal response?