An ideal gas in a container of volume 100 cm3 at 20°C has a pressure of 100 N/m2. Determine the number of gas molecules in the container
A)
2.4 × 106
B)
4.2 × 106
C)
6.0 × 1023
D)
2.5 × 1018
E)
5.2 × 1018
D
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A 50-kg satellite circles planet Cruton every 5.6 h in an orbit with a radius of 12 × 10^6 m. What is the magnitude of the gravitational force on the satellite by planet Cruton?
a. 63 N b. 58 N c. 68 N d. 73 N e. 50 N
Two mirrors are at right angles to one another. If an object is placed near the mirrors, what is the largest number of images that would be seen in the mirrors?
a. 3 b. 2 c. 4 d. 5 e. 6
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)
An encounter in which a large galaxy absorbs a smaller galaxy is referred to as
A. "Galactic cannibalism". B. "Galactic assimilation". C. "Galactic absorption". D. "Galactic merger".