What is the global positioning system (GPS)?
A) a system for determining positions on the Earth by careful observations of the Sun and stars
B) a system of determining positions on the Earth by receiving radio signals from many ground-based beacons
C) a system for determining positions on Earth using signals from a set of satellites in Earth orbit
D) a term used to refer to any type of celestial navigation
C
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A 120 kg mass is blown apart into an 80 kg piece and a 40 kg piece. After the blast, the two masses are moving apart with a relative velocity of 60 m/s. The total kinetic energy after the explosion is
A. 21 kJ. B. 35 kJ. C. 48 kJ. D. 56 kJ. E. 82 kJ.
When the Moon and the Sun lie exactly in the same direction in the sky, what phase of the Moon would you see?
A. gibbous B. full C. new D. half E. crescent
Which of the following statements about nuclear fusion is not true?
A. It involves two or more small atomic nuclei slamming into each other and sticking together to make a larger atomic nucleus. B. It refers solely to the process of converting hydrogen into helium. C. It is the process that has made most of the elements of which we and the Earth are made. D. It is the process that generates the energy by which our Sun shines.
When we see X-rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system
Which one would force us to immediately rule out the possibility of a black hole? A) bright X-ray emission that varies on a time scale of a few hours B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths C) sudden, intense X-ray bursts D) visible and ultraviolet light from the companion star