Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours
The change in brightness alternates between a small change and a large change. The most likely explanation is that ________.
A) the star is a member of an eclipsing binary star system
B) the star is periodically ejecting gas into space, every 73 hours
C) the star is a Cepheid variable
D) the star is a white dwarf
A
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A 400-g piece of metal at 120.0°C is dropped into a cup containing 450 g of water at 15.0°C
The final temperature of the system is measured to be 40.0°C. What is the specific heat of the metal, assuming no heat is exchanged with the surroundings or the cup? The specific heat of water is 4190 J/(kg ? K). A) 1470 J/(kg ? K) B) 2830 J/(kg ? K) C) 3420 J/(kg ? K) D) 3780 J/(kg ? K) E) 4280 J/(kg ? K)
According to modern scientific dating techniques, approximately how old is the solar system?
A) 10,000 years B) 4.6 million years C) 4.5 billion years D) 14 billion years
Protostars can be observed in
A) the Crab Nebula. B) the Andromeda Galaxy. C) the Orion Nebula. D) our Solar System. E) the Helix Nebula.
When it is struck by 240-nm photons, a material having a work function of 2.60 eV emits electrons. What is the maximum kinetic energy of the emitted electrons?
(c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J) A) 2.58 eV B) 5.18 eV C) 2.00 eV D) 4.21 eV