I3

1. A uniform metal rod of length / stays along the line of greatest slope on a roof inclined at an angle O with the horizontal. Coefficient of friction between the sheet and the roof is / (u > tane) and temperature coeffi- cient of linear expansion of the material of the rod is a. On a particular day, temperature of the environment increases by an amount AT and then decreases by the same amount during a span of 24 h. (a) How much and in which direction will the upper edge, the mass center and the lower edge of the rod shift during the period of temperature rise? (b) How much and in which direction will the upper edge, the mass center and the lower edge of the rod shift during the period of temperature fall? (c) What is the net shift in location of the rod during the complete cycle of temperature rise and fall