The weather channel reports that it is a hot, muggy day with an air temperature of 90°f, a 10 mph breeze out of the southwest, and bright sunshine with a solar insolation of 400 w/m2. consider the wall of a metal building over which the prevailing wind blows. the length of the wall in the wind direction is 10 m, and the emissivity is 0.93. assume that all the solar irradiation is absorbed, that the surroundings are at tsur = 85°f, and that flow is fully turbulent over the wall. estimate the average wall temperature.

When a charged balloon sticks to a wall, the downward gravitational force is balanced by an upward static friction force. the normal force is provided by the electrical attraction between the charged balloon and the equal but oppositely charged polarization induced in the wall's molecules. if the mass of a balloon is 1.2 g, its coefficient of static friction with the wall is 0.71, and the average distance between the opposite charges is 0.80 mm, what minimum amount of charge must be placed on the balloon in order for it to stick to the wall? express your answer to two significant figures and include appropriate units.