## Utility Pole

Consider a utility pole is constructed from a hollow circular tube of passivated aluminum to support a compressive load. The inner and outer diameters of the 144 inch long tube are 6 inches and 12 inches respectively. If the pole shortens by 0.025 inches due to its load, calculate the utility pole’s strain.

##
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__**Hint**

**Hint**

Strain is the change in length per unit length.

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__**Hint 2**

**Hint 2**

$$$\varepsilon=\frac{\Delta L}{L_o} $$$

where
$$\varepsilon$$
is the engineering strain,
$$\Delta L$$
is the change in length, and
$$L_o$$
is the original length.

Strain is the change in length per unit length.

$$$\varepsilon=\frac{\Delta L}{L_o} $$$

where
$$\varepsilon$$
is the engineering strain,
$$\Delta L$$
is the change in length, and
$$L_o$$
is the original length. Therefore:

$$$\varepsilon=\frac{-0.025in}{144in}=-0.00017$$$

Note: the length is reduced so the change in length needs to be negative, and that cross section does not impact strain.

-0.00017