a wood post 20 ft long shortens 1/4 in. under load determine the average unite strain

To determine the average unit strain, we need to divide the change in length by the original length. Let's go step by step:

- First, convert the length of the wood post from feet to inches. Since 1 foot equals 12 inches, multiplying 20 ft by 12 gives us 240 inches.

- Next, calculate the change in length. The post shortens 1/4 inch under load. So, for a 240-inch long post, the change in length is 1/4 inch.

- Now, divide the change in length by the original length. The change in length is 1/4 inch, and the original length is 240 inches. Therefore, the average unit strain is (1/4) / 240 = 1/960.

So, the average unit strain of the wood post under load is 1/960.