2.1

An 80-cm stretch cord is used to tie the rear of a canoe to the car hook, as shown in Figure P2.1. In the stretched position the cord forms the side AB of the triangle shown. Determine the average normal strain in the stretch cord.

Figure P2.1

2.2

The diameter of a spherical balloon changes from 250 mm to 252 mm (Figure P2.2). Determine the change in the average circumferential normal strain.

Figure P2.2

2.3

Two rubber bands are used for packing an air mattress for camping (Figure P2.3). The undeformed length of a rubber band is 7 in. Determine the average normal strain in the rubber bands if the diameter of the mattress is 4.1 in at the section where the rubber bands are on the mattress.

Figure P2.3

2.4

A canoe on top of a car is tied down using rubber stretch cords, as shown in Figure P2.4a. The undeformed length of the stretch cord is 40 in. Determine the average normal strain in the stretch cord assuming that the path of the stretch cord over the canoe can be approximated as shown in Figure P2.4b.

Figure P2.4

2.5

Due to the application of the forces in Figure P2.5, the displacements of the rigid plates in the x direction were observed as u _B = ?1.8 mm, u _c = 0.7 mm, and u _D = 3.7 mm. Determine the axial strains in the rods in sections AB,