Consider a situation where you exert a force F on a crate of mass m, moving it at a speed v a distance d across a floor in a time interval t. The work you do on the crate is Fv
Indicate whether the statement is true or false
F
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A stack 60 m high by 5 m in diameter has an average temperature of 300ºC on its outer surface when exhaust gases pass through it. Estimate the heat loss from the stack into still air at 25ºC.
What will be an ideal response?
Between July 1969 and December 1972, 17 people reached the surface of the Moon
a. True b. False Indicate whether the statement is true or false
In a lead-shot tower, spherical 0.95-cm-diameter BB shots are formed by drops of molten lead which solidify as they descend in cooler air. At the terminal velocity, i.e., when the drag equals the gravitational force, estimate the total heat transfer coefficient if the lead surface is at 171°C, the surface of the lead has an emissivity of 0.63, and the air temperature is 16°C. Assume CD = 0.75 for the first trial calculation.
GIVEN
• Spherical lead-shot falling through the air at terminal velocity
• Shot diameter (D) = 0.95 cm = 0.0095 m
• Lead surface temperature (Ts) = 171°C = 494 K
• Lead surface emissivity (?) = 0.63
• Air temperature (T?) = 16°C 289 K
• Assume CD = 0.75 for the first trial calculation FIND
• The total average heat transfer coefficient (htotal). ASSUMPTIONS
• The surroundings act as a black body enclosure at T?
SKETCH
A statue that is 10.4 cm tall is placed 4.8 cm in front of a concave lens. The image is 4.0 cm from the lens. How tall is the image?
A) 13 cm B) 8.7 cm C) 5.4 cm D) 1.8 cm