One star is three times further away than another. The parallax angle of the more distant star is:
A. nine times larger than that of the nearer star
B. three times larger than that of the nearer star
C. the same as that of the nearer star
D. three times smaller than that of the nearer star
E. nine times smaller than that of the nearer star
Answer: D. three times smaller than that of the nearer star
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The temperature of air flowing through a 25-cm-diameter duct whose inner walls are at 320°C is to be measured with a thermocouple soldered in a cylindrical steel wall of 1.2-cm-OD with an oxidized exterior, as shown in the accompanying sketch. The air flows normal to the cylinder at a mass velocity of 17,600 kg/(h m2). If the temperature indicated by the thermocouple is 200°C, estimate the actual temperature of the air.
GIVEN
• Cylindrical thermocouple wall in an air duct
• Duct diameter (Dd) = 25 cm = 0.25 m
• Duct wall temperature (Tds) = 320°C =m 593 K
• Wall outside diameter (Dw) = 1.2 cm = 0.012 m
• Exterior of wall is oxidized
• Air mass velocity /m A
= 17,600 kg/(h m2)
• Thermocouple indicated temperature (Ttc) = 200°C = 473 K
FIND
• Air temperature (T?) ASSUMPTIONS
• Steady state
• Thermal resistance between the thermocouple and the wall exterior surface is negligible
• Inside of duct behaves as a black body enclosure
• Conduction to the thermocouple wall from the duct wall can be neglected
PROPERTIES AND CONSTANTS
the emissivity of oxidized steel (?) = 0.94. From Appendix 1, Table 5, the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)
A series of n uncharged concentric shells surround a small central charge q. The charge distributed on the outside of the nth shell is
a. ?nq. b. ?(ln n)q. c. +q. d. +(ln n)q. e. +nq.
A stage 4 object can be plotted on the H-R diagram. At this stage, the star will appear:
A) in the middle left of the diagram. B) in the middle right of the diagram. C) just on the bottom right of the main sequence. D) down and to the left of where it will be when it is a main sequence star. E) in the middle of the main sequence.
The support force on a 10-N book that rests on a horizontal surface is
A) less than 10 N. B) 10 N. C) greater than 10 N. D) dependent on whether the book lies flat or stands upright.