EM 319 Mechanics of Solids
Fall 2010
Homework #2
Due: 9/9/2010
1. Find the change of length of the entire structure, given that:
E
AB
= 2
E
,
E
BC
=
E
,
E
CD
= 3
E
,
A
AB
=
A
,
A
BD
= 2
A
.
Solution:
FBDs
EQM
P
P
P
P
P
P
F
ED
CE
BC
AB
x
2
0
Change of length
EA
PL
A
E
L
P
A
E
L
P
A
E
L
P
A
E
L
P
A
E
L
P
A
E
L
P
A
E
L
P
A
E
L
P
ED
ED
ED
ED
CE
CE
CE
CE
BC
BC
BC
BC
AB
AB
AB
AB
ED
CE
BC
AB
2
)
2
)(
3
(
)
2
(
)
2
)(
3
(
)
2
)(
(
)
2
(
)
2
(
)
(
)
2
(
)
(
total
(negative sign means the whole structure gets shorter)
2
P
L
P
A
B
D
1/2
L
3
P
C
1/2
L
L
E
P
AB
P
A
A
B
P
BC
P
A
B
P
CE
C
P
P
ED
2
P

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