13. In a large hall, a pendulum is to be made by suspending a 40-kg ball from the end of steel wire 15 m long. Tensile strength of steel is 0.48 x 10' Pa. and Y is 200 x 10° Pa.
a. What cross-sectional area should the wire have if the applied stress in it is to be only
10% of its breaking stress? [8.1 x 10-6 mº]
b. How far will the ball stretch? [3.6 mm]