Briefly explain why sunspots are cooler than surrounding regions of the Sun, and why they look dark in photos
What will be an ideal response?
They are cooler because their strong magnetic fields suppress convection and prevent hotter material from flowing into them. Because they are cooler, they emit less thermal radiation per unit area and therefore look dark in contrast to brighter surrounding regions.
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Astronomers conclude that quasars must come from the earliest phases of the Universe because they ____
a. have supermassive black holes b. are colliding with other galaxies c. create jets d. have large redshifted spectra e. have a fluctuating luminosity
Gravitational Potential Energy: Three masses are located as follows: a 3.5-kg mass is at the origin, a 4.2-kg mass at (0.0 m, 7.0 m), and a 6.5-kg mass at (24.0 m, 0.0 m). What is the gravitational potential energy of this system of masses? (G = 6.67 × 10-11 N ? m2/kg2)
A. -2.8 × 10-10 J B. -2.0 × 10-10 J C. -1.4 × 10-10 J D. -3.2 × 10-10 J E. -3.9 × 10-10 J
If you walk towards a mirror at a certain speed, the relative speed between you and your image is
A) half your speed. B) your speed. C) twice your speed. D) none of the above
A square loop of wire has a current going around it. The magnetic field from the current on each side of the loop results in a magnetic force on the wire on the opposite side. Each resulting magnetic force on the opposite side wire
a. pushes inward on the loop. b. is actually zero since a current cannot push on itself. c. depends on whether the current is clockwise of counterclockwise. d. pushes outward on the loop.