Ametallic airfoil of elliptical cross section has a mass of 50 kg, surface area of 12 m2, and a specific heat of 0.50 kj/kg·k. the airfoil is subjected to air flow at 1 atm, 25°c, and 5 m/s along its 3-m-long side. the average temperature of the airfoil is observed to drop from 160°c to 150°c within 2 min of cooling. assuming the surface temperature of the airfoil to be equal to its average temperature and using momentum-heat transfer analogy, determine the average friction coefficient of the airfoil surface.

In a stagnant pool of water, a crayfish may spend much of its time lying with one side of its carapace near the surface of the water. in this position, it will move the walking legs on that side in a rhythmic back-and-forth motion. explain the likely function of this behavior.

Because air contracts as it cools, the air pressure inside a freezer is typically lower than on the outside. why do ice cubes inside a freezer tend to shrink over time? a. the ice dissolves oxygen from the air, forming a denser crystalline matrix.b. the ice reacts chemically with carbon dioxide in the air, forming gaseous carbon compounds.c. the ice melts, and then the liquid freezes as ice crystals on the bottom of the freezer.d. the ice sublimes, and then the water vapor deposits as ice crystals on the sides of the freezer.

Aheavy piece of hanging sculpture is suspended by a90-cm-long, 5.0 g steel wire. when the wind blows hard, the wire hums at its fundamental frequency of 80hz. what is the mass of the sculpture?