Sirius, the brightest star in the night sky, is actually a binary star system. Sirius A is main-sequence star and Sirius B is a white dwarf. Nearly all the visible light we see from Sirius comes from Sirius A. But when we photograph the system with x-ray light, as shown here, Sirius B is the brighter of the two stars. Why?
A) As a white dwarf, Sirius B is much hotter than Sirius A and thus emits more x-rays.
B) As a white dwarf, Sirius B is too small to emit visible light but not too small to emit x-rays.
C) Sirius B is brighter in x-rays because it is a nova.
D) Sirius B is brighter in x-rays because it is a white dwarf supernova.
A) As a white dwarf, Sirius B is much hotter than Sirius A and thus emits more x-rays.
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A 600-kg car makes a 90° turn. Its speed before the turn is 21.0 m/s and after the turn it is 24.0 m/s. What is the magnitude of the change in the car's momentum during the turn?
A) 19.1 × 103 kg?m/s B) 10.2 × 103 kg?m/s C) 9.55 × 103 kg?m/s D) 12.0 × 103 kg?m/s E) 22.2 × 103 kg?m/s
When a bar magnet is broken in half, the strength of the four new poles relative to pole strength before breaking is
A) less than half. B) half. C) the same. D) somewhat more.
Dean teaches that the phenomenon of regelation is due to the
A) freezing point of water. B) melting point of ice. C) open-structured nature of ice crystals. D) high specific heat of water.
The clearest images of Uranus shown in the text have been obtained using:
A) the Hubble Space Telescope. B) infrared ground- based telescopes at the Keck Observatory. C) the Pioneer Spacecraft. D) the Cassini Spacecraft. E) visible light ground-based telescopes at the European Southern Observatory.