Rule

As the extension or compression of the length of any substance is to its length, so is the weight that pro-dueed that extension or compression to the modulus of elasticity in pounds avoirdupois.

Example

Tf a bar of cast-Iron, 1 inch square and 10 feet in length, is extended .008 inch, with a weight or 1000 lbs., what is the weight of its modulus of elasticity?

.008 :120 (10X12):: 1000:15.000,000 lbs.

Note

When the weight of the modulus of elasticity of a substance is known, the height of it can be readily computed by dividing the weight by the weight of a bar of the substance 1 inch square and 1 foot in length.

Ex. 2

If a wrought-iron chain, 60 feet in length and .2 inch in diameter, is subjected to a strain of 150 lbs., what will it be extended?

The modulus of elastlcity of iron wire is 26,808,000 lbs., and the area of chain .22X'.7854=.31416. 150

-------=477,463 lbs. per square inch, and 60x12=720 ins.

.31416

120 343.773 36

Then 477.463X------------=------------=.0128 inch.

26,808,000 26,808,000