Which two quantities must you know in order to plot a star on an H-R diagram?
A) mass and lifetime
B) surface temperature and luminosity
C) mass and radius
D) apparent brightness and distance
B) surface temperature and luminosity
You might also like to view...
Energy in the Electric Field: A -6.5-µC point charge is 8.0 cm from a -17-µC charge. What is the electric energy density at the point midway between them? (?0 = 8.85 × 10-12 C2/N ? m2, k = 1/4??0 = 9.0 × 109 N ? m2/C2)
Fill in the blank(s) with the appropriate word(s).
Sara lies on a bed of sharp nails without harm because
A) many of the nails don't make contact with her body. B) her weight is distributed over hundreds of nails. C) she exercises mind over matter. D) none of the above
An 800-kHz radio signal is detected at a point 9.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.23 V/m
Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the average electromagnetic energy density at that point? (c = 3.0 × 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2 ) A) 2.3 × 10-13 J/m3 B) 9.4 × 10-13 J/m3 C) 4.7 × 10-13 J/m3 D) 3.3 × 10-13 J/m3 E) 6.6 × 10-13 J/m3
A 1-cm-thick, 1-m-square steel plate is exposed to sunlight and absorbs a solar flux of 800 W/m2. The bottom of the plate is insulated, the edges are maintained at 20°C by water-cooled clamps, and the exposed face is cooled by a convection coefficient of 10 W/(m2 K) to an ambient temperature of 10°C. The plate is polished to minimize reradiation. Determine the temperature distribution in the plate using a node spacing of 20 cm. The thermal conductivity of the steel is 40 W/(m K).
GIVEN
Square plate with water-cooled edges exposed to solar flux
FIND
(a) Temperature distribution in the plate
ASSUMPTIONS
(a) Neglect temperature gradients through the plate thickness
SKETCH
