You discover a binary star system in which one member is a15MSun main-sequence star and the other star is a 10MSun giant. How do we believe that a star system such as this might have come to exist?
A) The giant must once have been the more massive star but transferred some of its mass to its companion.
B) Despite the low odds of finding a system with two such massive stars, there is nothing surprising about the fact that such systems exist.
C) The two stars probably were once separate but became a binary when a close encounter allowed their mutual gravity to pull them together.
D) The main-sequence star probably is a pulsating variable star and therefore appears to be less massive than it really is.
E) Although both stars probably formed from the same clump of gas, the more massive one must have had its birth slowed so that it became a main-sequence star millions of years later than its less massive companion.
A
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A solid concrete wall has dimensions 4.0 m × 2.4 m and is 30 cm thick. The thermal conductivity of the concrete is 1.3 W/m ? K, and it separates a basement from the ground outside
The inner surface of the wall is at 18°C, and the outside surface is at 6°C. How much heat flows through the wall every hour? A) 1.8 MJ B) 1.8 kJ C) 500 J D) 5.0 MJ E) 5.0 kJ
A) Explain which star is apparently brighter to you as viewed from Earth on a clear night, a star with a negative value or a star with a positive value. b) If star A has an apparent visual magnitude that is more negative than star B, which is the brighter star?
What will be an ideal response?
Near the earth the intensity of radiation from the sun is 1.35 kW/m2. What volume of space in this region contains 1.0 J of electromagnetic energy? (c = 3.0 × 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A) 4.5 × 10-6 m3 B) 3300 m3 C) 7.4 × 10-4 m3 D) 1400 m3 E) 220,000 m3
A distant palm tree on a hot dry day that often appears to be reflected from water is
A) due to light refracted upward as it grazes the hot surface. B) the inverse of a mirage. C) evidence that light travels in straight lines.