You discover a binary star system in which one member is a 15MSun main-sequence star and the other star is a 10MSun giant. Why should you be surprised, at least at first?
A) It doesn't make sense to find a giant in a binary star system.
B) The odds of ever finding two such massive stars in the same binary system are so small as to make it inconceivable that such a system could be discovered.
C) The two stars in a binary system should both be at the same point in stellar evolution; that is, they should either both be main-sequence stars or both be giants.
D) The two stars should be the same age, so the more massive one should have become a giant first.
E) A star with a mass of 15MSun is too big to be a main-sequence star.
D
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a. 159% b. 259% c. 359% d. 459% e. The correct answer is not given.
The type of radiation that fogged Becquerel’s photographic plates was probably
A. Alpha radiation. B. Beta radiation. C. Gamma radiation. D. Either alpha or beta radiation. E. Either beta or gamma radiation.
A car runs into a brick wall. The collision pushes in the car’s front end about a meter. Is the work done on the car by the contact interaction between it and the wall positive, negative, or zero?
A. Positive B. Negative C. Zero D. One needs more information to answer.
Which of the following is not true of quasars?
A) Quasars were more common in the past. B) The light produced by quasars comes from an accretion disk surrounding a supermassive black hole. C) Quasars are powered by the intense production of large numbers of stars that can only be sustained for a relatively short time. D) Some quasars can change their brightness on the timescale of hours. E) Some quasars are more than a thousand times more luminous than the Milky Way.