As the Moon covers the solar disk during a solar eclipse, a flash spectrum of the Sun's chromosphere can be recorded. This flash spectrum reveals an emission spectrum and provides information on the properties of the chromosphere. As the Moon moves from the inner chromosphere to the outer chromosphere, the spectral lines present in the flash spectrum change. What is going on in the chromosphere
that produces the changes in the flash spectrum? I. The temperature of the chromosphere decreases as the distance from the photosphere increases. II. The temperature of the chromosphere increases as the distance from the photosphere increases. III. The density of the chromosphere decreases as the distance from the photosphere increases. IV. The density of the chromosphere increases as the distance from the photosphere increases.
a. I & III
b. I & IV
c. II & III
d. II & IV
e. I
c
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Magnetic particle inspection can detect only _________cracks.
Fill in the blank(s) with the appropriate word(s).
Suppose we subject a golf ball and a more massive lead ball to identical net forces. Then, compared to the golf ball, the lead ball must have
A) a larger acceleration. B) a larger speed. C) a smaller speed. D) a smaller acceleration. E) None of the above answers is necessarily true.
Develop an expression for the ratio of the rate of heat transfer to water at 40°C from a thin flat strip of width ?D/2 and length L at zero angle of attack and a tube of the same length and diameter D in cross-flow with its axis normal to the water flow in the Reynolds number range between 50 and 1000. Assume both surfaces are at 90°C. for air flowing over the same two surfaces in the Reynolds number range between 40,000 and 200,000. Neglect radiation.
GIVEN • Air flowing over a thin flat strip at zero angle of attack or a tube in crossflow • Air temperature (T?) = 40°C • Tube diameter = D • Strip width = ?D/2 • Tube and strip length = L • Reynolds number : 40,000 < Re < 200,000 FIND • The ratio of the heat transfer from the strip and that from the cylinder. (qs/qt) ASSUMPTIONS • Radiative heat transfer is negligible • Steady state for both cases • The tube and strip temperatures (Ts) are 90°C PROPERTIES AND CONSTANTS Kinematic viscosity (?) = 17.6 × 10–6 m2/s Prandtl number (Pr) = 0.71 at 90°C Prs = 0.71
Mort and Velma are twins, born at the same time on Earth. Velma is taken on a long trip into outer space, at a speed close to lightspeed, and returns to Earth. When she returns,
A) Mort observes that he is younger than Velma, but Velma will observe that she is younger than Mort. B) Mort and Velma observe that they have aged equally. C) Mort observes that he is older than Velma, and Velma observes that she is older than Mort. D) Mort and Velma both observe that Velma is older than Mort. E) Mort and Velma both observe that Mort is older than Velma.