Imagine an advanced civilization living on a planet orbiting at a distance of 10 AU (1.5 billion kilometers) from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole
The black hole is surrounded by an accretion disk. Sometime within the next million years or so, the civilization's planet is likely to be doomed because A) the red giant will probably supernova within the next million years.
B) jets of material shot out of the accretion disk will shoot down their planet.
C) the red giant star, which provides most of energy the civilization needs to exist, will soon be destroyed in the accretion disk.
D) tidal forces from the black hole will rip the planet apart.
A
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Titan has oceans made chiefly of liquid ________, along with smaller amounts of methane and propane
Fill in the blank(s) with correct word
A car enters a level, unbanked semi-circular hairpin turn of 300 m radius at a speed of 40 m/s. The coefficient of friction between the tires and the road is ? = 0.25. If the car maintains a constant speed of 40 m/s, it will
A. attempt to dig into the road surface. B. tend to veer toward the center of the semicircle. C. arrive safely at the end of the semicircle. D. tend to veer toward the outside of the circle. E. veer toward the center for the first quarter-circle, then veer toward the outside for the second quarter-circle.
The wheelbase on a 50,000-kg truck is 2.40 m wide and the truck's center of mass is located along the vertical centerline of the truck and 2.00 m above the bottom of the tires. The truck is going around a horizontal turn with a radius of 180 m
What is the maximum speed at which the truck can go around the curve without some of its tires lifting off the road? A) 44.3 m/s B) 38.2 m/s C) 32.5 m/s D) 28.2 m/s E) 25.0 m/s
Which of the half-reactions below would be complementary and balance the following half-reaction?
Zn+2 ? Zn A) Cu ? Cu+2 B) K+ ? K C) 2 Cu ? 2 Cu+2 D) 2 K+ ? 2 K E) Cl2 ? 2 Cl-