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 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?
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Which of the following is not true of quasars?
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By how much is the energy stored in a Hooke's law spring increased when its stretch is increased from 7.00 cm to 15.00 cm?
a. 159% b. 259% c. 359% d. 459% e. The correct answer is not given.