Which of the following statements is true of the analysis called helioseismology?
A) The solar interior is observed using the light that emerges from below the photosphere.
B) The cause of the 22-year cycle of sunspots is studied using the Sun's unchanged magnetic field.
C) The vibrations in the Sun are used by solar astronomers to explore its depths.
D) The unaltered electron orbits are detected when an atom is in a magnetic field.
C
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A 20.0 cm wrench is used to generate a torque at a bolt. A force of 50 N is applied perpendicularly at the end of the wrench. The torque generated at the bolt is
A. 8.0 N•m. B. 10 N•m. C. 14 N•m. D. 22 N•m. E. 37 N•m.
Suppose you are looking at the sky at about midnight on the December solstice. Based on the given right ascensions and declinations, which of the following stars will be nearest to your meridian? Assume you live at a latitude where all the stars on this list rise above your horizon each day. (Hint: Recall that the Sun's celestial coordinates on the December solstice are RA = 18h, dec = -23-1/2°.)
A) Spica: RA = 13hr 25m, dec = -11°09' B) Deneb: RA = 20hr 41m, dec = +45°16' C) Sirius: RA = 6hr 45m, dec = -16°42' D) Alpha Centauri: RA = 14hr 40m, dec = -60°50' E) Vega: RA = 18hr 37m, dec = +38°47'
If Jupiter were about 80 times more massive than it is, nuclear fusion should have been possible, making it a small star. What might have been the most likely effect on the Earth?
A) The gravitational pull might have prevented the Earth settling into a stable orbit, which would have prevented the development of life on Earth. B) Jupiter's moons would have been likely to develop life, which would have competed with life on Earth. C) The extra radiation from a second star in the solar system would have prevented life forming on Earth. D) Jupiter's magnetic field would have been much larger, disrupting Earth's magnetic field. E) Nothing because Jupiter is so much further from the Earth than the Sun is.
A large 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on the one side is 28 W/(m2 K) and on the other side is 57 W/(m2 K). If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it will take for the copper plate to reach a temperature of 82°C.
GIVEN
• A large copper plate between two air streams whose temperatures suddenly change
• Plate thickness (2L) = 2.54 cm = 0.0254 m
• The heat transfer coefficients are
? lch = 28 W/(m2 K)
? 2ch = 57 W/(m2 K)
• Air temperature changes from 38°C to 93°C
FIND
• How long it will take for the copper plate to reach a temperature of 82°C
ASSUMPTIONS
• The initial temperature of the plate is 38°C
• The plate can be treated as an infinite slab
SKETCH
