_______________ variable stars are useful in measuring the distance to globular clusters
Fill in the blank(s) with correct word
Cepheid
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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
Cold dust disks are _____________ disks around main-sequence stars, the dust of which is created by collisions among the planetesimals
Fill in the blank(s) with correct word
If light bounces off the surface of a material, the change in direction is called:
a. Reflection b. Refraction c. Interference d. Diffusion
Experimenting is part of the scientific method
a. True b. False Indicate whether the statement is true or false