____ are believed to have formed on Mercury when the planet's interior cooled and shrank
a. Jumbled terrain
b. The highlands
c. Maria
d. Lobate scarps
e. Sinuous rilles
D
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In what part of spiral galaxies do new stars form?
A) In the bulge. B) In the spiral arms. C) No new stars are forming anywhere. D) In the halo. E) No new stars form inside spirals. They form outside the galaxy and are pulled in.
What happens to the velocity of sound in a gas when the absolute temperature of that gas is doubled?
A) It doubles. B) It stays the same. C) It increases to 1.41 times its original value. D) It quadruples.
The assumption of homogeneity states that
a. the Universe looks the same at all epochs. b. the Universe looks the same from all locations over sufficiently great distances. c. the Universe looks the same in all directions over sufficiently great distances. d. the Universe looks the same at all epochs, the Universe looks the same from all locations over sufficiently great distances, and the Universe looks the same in all directions over sufficiently great distances. e. None of the other choices are correct.
The heat loss from the hairdryer duct enclosure was neglected. To a designer, while this may appear to be reasonable assumption it should really be checked bu order of magnitude calculations even if all the parameters are not known. In order to determine whether the heat loss from the exterior of the duct enclosure is neglected or not, assume a high surface emissivity of 0.8, an average surface temperature of 400C, and consider an estimate for natural convection coefficient at a high reasonable value. If the length of hair dryer is 20 cm, calculate the expected heat loss per unit length of the dryer duct, compare it with heat dissipation per unit length from the internal electrical heating, and comment on validity of negligible heat loss assumption.
GIVEN - High surface emissivity of 0.8, an average surface temperature of 400C - Length of the hear drier L=20 cm =0.2 m FIND - Expected heat loss per unit length of dryer duct - Compare it with heat dissipation per unit length from the internal electrical heating. ASSUMPTIONS - Steady state conditions prevail - Heat loss from outside of dryer duct is neglected. PROPERTIES AND CONSTANTS the air properties are Convection heat transfer coefficient for air (considering higher value) (hc)=20 W/(m2 K) Specific heat capacity(Cp)= 1.0049 kJ/kgK