Most SETI searches are done at:
A) X-ray wavelengths.
B) infrared wavelengths.
C) visual wavelengths.
D) radio wavelengths.
E) gamma wavelengths.
D
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A person looking through eyeglasses sees
a. real images. b. virtual images. c. erect images. d. inverted images. e. polarized images.
A pocket of air moving south in the Northern Hemisphere will be deflected ________ by the rotation of Earth?
A. to the east B. to the south C. upward to a higher altitude D. downward toward the surface E. to the west
A batter hits a home run in which the ball travels 110 m horizontally with no appreciable air resistance. If the ball left the bat at 50° above the horizontal just above ground level, how fast was it hit?
What will be an ideal response?
An architect is asked to determine the heat loss through a wall of a building constructed as shown in the sketch. The space between wall is 10 cm and contains air. If the inner surface is at 20°C and the outer surface is at – 8°C, (a) estimate the heat loss by natural convection. Then determine the effect of placing a baffle (b) horizontally at the mid- height of the vertical section (B), (c) vertically at the center of the horizontal section (C), and (d) vertically half-way between the two surfaces (D).
GIVEN
• Air filled wall construction as shown above
• Inner wall temperature (Ti) = 20°C
• Outer wall temperature (To) = – 8°C
• Wall spacing (?) = 10 cm = 0.1 m
• Wall height (L) = 3 m
• Wall width (w) = 6 m
FIND
The rate of heat loss by natural convection (qc) for the wall (a) without baffles (b) with a horizontal baffle at a mid-height of the wall-baffle B (c) with a vertical baffle at the center of the horizontal section-baffle C (d) with a vertical baffle midway between the walls-baffle D
ASSUMPTIONS
• Wall temperatures are constant and uniform
• Steady state conditions
• Baffle thickness is negligible
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 6°C
Thermal expansion coefficient (?) = 0.00359 1/K
Thermal conductivity (k) = 0.0241 W/(m K)
Kinematic viscosity (?) = 14.4 × 10–6 m2/s
Prandtl number (Pr) = 0.71