Collisions between galaxies are thought to:
A) have stopped about 5 billion years ago.
B) be commonplace.
C) have never occurred.
D) be extremely rare.
E) have only occurred between 10 and 15 billion years ago.
B
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_______________ objects are asteroids with orbits that carry them into the inner Solar System
Fill in the blank(s) with correct word
Within a given system, the internal forces
A. are always balanced by the external forces. B. all add to zero. C. are only determined by subtracting the external forces from the net force on the system. D. determine the motion of the system. E. are measured with a gravimeter.
Suppose that at a certain time a quanton has a well-defined position x = 0.15 nm. At that time, we perform an experiment to determine the quanton’s momentum, and find it has a value that corresponds to a de Broglie wavelength of 0.45 nm to a high degree of precision. What can we say about the quanton’s position after the experiment?
A. It is still 0.15 nm. B. It is now 0.45 nm. C. It is now within ±0.45 nm of 0.15 nm. D. It is now undefined but probably close to 0.15 nm. E. It is now completely undefined. F. Other (specify).
In designing buildings to be erected in an area prone to earthquakes, what relationship should the designer try to achieve between the natural frequency of the building and the typical earthquake frequencies?
A) The natural frequency of the building should be exactly the same as typical earthquake frequencies. B) The natural frequency of the building should be very different from typical earthquake frequencies. C) The natural frequency of the building should be almost the same as typical earthquake frequencies but slightly higher. D) The natural frequency of the building should be almost the same as typical earthquake frequencies but slightly lower.