22
MOLESWORTH S POCKET-BOOK
. . . • Modulus oj Elabticitx-
The modulus of elasticity of any material is the force that
would lengthen a bar of that material of 1 inch
double its length, or would compress it till.its length beca,
zero - supposing it possible to stretch or compress the bar
?o this extreme extent without breaking it andH.W the
following relation between stress and strain held good .
a = Alteration in length due to any force F less than the
modulus. .
A ä Alteration due to the modulus h.
a _F
. A E
To find the Compression ok - Extension or any Bo»J
UNDER A GIVEN STRAIN WITHIN ITS LIMITS OF El-Afc-
TICTTT. W. ’
(See next page).
L = Length in feet of body strained.
I = Increase or decrease of length in feet caused by a
strain/. . . ,
f = Force of the strain in lbs. per square meh.
E = Modulus of elasticity (for values of E see next page).
b L/ Lf 11. IB •
=S —r- ,
DETERMINATION OF E FROM THE
FREELY SUPPORTE» AT ENDS AND LOADED AT CENTS .
I = Clear distance between supports in inches.
c = Breadth of beam in inches.
d = Depth of beam in inches.
W = Weight in lbs.
x - Deflection In inches produced by W.
WZ^
E~4bd’»‘