Two numbers, one with 4 significant figures and the other with 3 significant figures, are combined using the math operations given below. Which operation can give a result with fewer than 3 significant figures?
a. addition
c. multiplication
b. subtraction
d. division
B
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Evaluate the Prandtl number from the data below
GIVEN
FIND
The Prandtl number (Pr)
Consider a planet orbiting a Sun-like star that has been detected by the Doppler and that has an orbital period of one year. The larger the velocity changes measured for the star, the
A) larger the mass of the planet. B) larger the radius of the planet. C) smaller the mass of the planet. D) smaller the radius of the planet.
All the chemical energy in food is converted into running the body's metabolism
What will be an ideal response?
A copper sphere 2.5 cm in diameter is suspended by a fine wire in the center of an experimental hollow cylindrical furnace whose inside wall is maintained uniformly at 430°C. Dry air at a temperature of 90°C and a pressure of 1.2 atm is blown steadily through the furnace at a velocity of 14 m/s. The interior surface of the furnace wall is black. The copper is slightly oxidized, and its emissivity is 0.4. Assuming that the air is completely transparent to radiation, calculate for the steady state (a) the convection heat transfer coefficient between the copper sphere and the air, and (b) the temperature of the sphere.
GIVEN
• A copper sphere suspended in a furnace with air flowing over it
• Sphere diameter (D) = 2.5 cm = 0.025 m
• Sphere emissivity (?) = 0.4
• Furnace wall temperature (Tw) = 430°C = 703 K
• Air temperature (Ta) = 90°C = 363 K
• Air pressure (pa) = 1.2 atm
• Air velocity (U?) = 14 m/s FIND (a) The convective heat transfer coefficient ( ) ch (b) The temperature of the sphere (Ts) ASSUMPTIONS
• Steady state
• The air behaves as an ideal gas
• The furnace can be treated as a black body enclosure
• Only the density of the air varies with temperature
SKETCH
