What do astronomers think is the eventual fate of a white dwarf?
What will be an ideal response?
As it radiates energy into space, a white dwarf's temperature gradually falls, but it can't shrink any smaller because its degenerate electrons resist getting closer together. Degenerate matter is a very good thermal conductor, so as heat flows to the surface and escapes into space the white dwarf gets fainter and cooler, moving downward and to the right in the H-R diagram. Because a white dwarf contains a tremendous amount of heat, it needs billions of years to radiate that heat through its small surface area. Eventually, such objects may become cold and dark, so-called black dwarfs.
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Suppose that Earth's rotation axis were tilted by 45 degrees instead of 23.5 degrees. Which of the following would be true, and why?
A) The seasons would be more extreme, because the Sun's rays would be more direct in summer and less direct in winter. B) The seasons would be more extreme, because the Earth's surface would be closer to the Sun in the summer and farther from the Sun in the winter. C) The seasons would be less extreme, because the Sun's rays would be less direct in summer and more direct in winter. D) The seasons would be less extreme, because the Earths' surface would be farther from the Sun in the summer and closer to the Sun in the winter.
An air-track cart is attached to a spring and completes one oscillation every 5.67 s in simple harmonic motion
At time t = 0.00 s the cart is released at the position x = +0.250 m. What is the position of the cart when t = 29.6 s? A) x = 0.0461 m B) x = 0.210 m C) x = 0.218 m D) x = 0.342 m E) x = -0.218 m
A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20.0 s. It is then turned off and coasts to a stop in 40.0 s. In the 60.0 s of rotation, through how many revolutions did the fan turn?
a. 251 b. 377 c. 126 d. 188
Two nuclei have the same number of protons but different numbers of neutrons. We call these two nuclei
A. ions. B. atomic mass units. C. isotopes. D. isobars.