A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point
A) down the ramp.
B) up the ramp.
C) vertically downward.
D) perpendicular to the ramp.
E) None of the above choices is correct.
E
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According to quantum theory,
A) individual microscopic events are inherently unpredictable. B) nature is "non-local," i.e., instantaneously connected across a distance. C) Both of the above. D) the overall statistics of large numbers of microscopic events are inherently unpredictable. E) All of the above.
Why do astronomers believe that Triton is a captured moon?
A) Triton is very small and potato-shaped, which is common of captured moons. B) Triton is too large to have been formed in the "miniature solar nebula" thought to have surrounded Neptune in its very early history. C) Triton appears to be made mostly of ice. D) Triton orbits Neptune in a direction opposite that of Neptune's rotation.
After the switch is closed in a series LR circuit, what is the current when a time equal to four time constants has elapsed?
A. (1/5) Imax B. (15/16) Imax C. (1/16) Imax D. 0.018 Imax E. 0.98 Imax
Why is the nucleosynthesis era so important in determining the chemical composition of the universe?
A) We can study the processes that occurred during the nucleosynthesis era to determine how most of the elements in the universe were created. B) By knowing how much matter was created during the nucleosynthesis era, we can determine whether the universe is open or closed. C) We can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe. D) All the elements except hydrogen were produced in the nucleosynthesis era. E) Except for a small amount of elements heavier than helium produced later by stars, the chemical composition of the universe is the same now as at the end of the nucleosynthesis era.