Telephone and electrical lines are allowed to sag between poles so that the tension will not be too great when something hits or sits on the line.
(a) Is it possible to have the lines perfectly horizontal? Why or why not?
(b) Suppose that a line were stretched almost perfectly horizontally between two poles that are 30 m apart. If a 0.25-kg bird perches on the wire midway between the poles and the wire sags 1.0 cm, what would be the tension in the wire? (Neglect the mass of the wire.)