Question

The bar in the figure has constant cross sectional area A. The top third of the bar, of length L, is made of a material with mass density ρ and Young's modulus E. The bottom two thirds of the bar (length 2L) is made of a different material, with density ρ/2 and Young's modulus 2E. The bar is fixed at the floor, C, at x=3L, and at the ceiling, B, at x=0. The bar deforms under its own weight. For a material with density ρ, gravity results in a load per unit volume ρg. No other loads are applied.
A , L , E , ρ , and g are KNOWN quantities.
Note that you must consider the gravity load on both segments of the bar as densities are different but comparable.
Q1_1_1 : 40.0 POINTS
Find a symbolic expression for the distributed load per unit length due to gravity fx(x), in terms of ρ, g, A (with ρ as rho):

for 0≤x<L, fx(x)=

unanswered

for L<x≤3L, fx(x)=

unanswered
You have used 0 of 3 submissions
Q1_1_2 : 100.0 POINTS
Use the force method for statically indeterminate structures to obtain a symbolic expression for the reaction RCx at the support C in terms of ρ, g, A, L (with ρ written as rho):

RCx=

unanswered
You have used 0 of 3 submissions
Q1_1_3 : 40.0 POINTS
Obtain a symbolic expression for the axial force in the bar N(x) in terms of ρ, g, A, L, x (with ρwritten as rho):

for 0≤x<L, N(x)=

unanswered

for L<x≤3L, N(x)=

unanswered
You have used 0 of 3 submissions
Q1_1_4 : 80.0 POINTS
Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written asrho). (Note: enter the expressions for the stresses with their appropriate signs.)

σmax,Tn=

unanswered

at location xmax,T=

unanswered

σmax,Cn=

unanswered

at location xmax,C=

unanswered
You have used 0 of 3 submissions
Q1_1_5 : 60.0 POINTS
Obtain a symbolic expression for the displacement ux(x=2L) in terms of ρ, g, E, L (with ρwritten as rho):

ux(x=2L)=

unanswered
You have used 0 of 3 submissions
Q1_2 (QUIZ 1 PROBLEM 2): STATICALLY INDETERMINATE TRUSS PROBLEM WITH THE METHOD OF JOINTS
The truss in the figure is composed by 4 bars (AD, AC, BC, CD) connected by pins at A,B,C,D. The geometry of the truss is defined in the figure in terms of the length H of bar BC. A vertical load W=400kN is applied at joint D. A horizontal load 2W=800 kN is applied at joint C. The material of bar AC has modulus E0 and cross sectional area A0.
Q1_2_1 : 100.0 POINTS
(a) Use the method of joints to obtain the numerical values (in kN) of the axial forces in the four bars.
Note: there will be factors of 2√ in your solutions. Do not use the square root symbol in your answer, just factor in the value as 1.4142

NAD=

kN
unanswered


NAC=

kN
unanswered


NBC=

kN
unanswered


NCD=

kN
unanswered

You have used 0 of 3 submissions
Q1_2_2 : 100.0 POINTS
(b) Obtain the value of the Cartesian components of reactions at the supports in kN.

RAx=

kN
unanswered


RAy=

kN
unanswered


RBx=

kN
unanswered


RBy=

kN
unanswered

You have used 0 of 3 submissions
Q1_2_3 : 40.0 POINTS
Obtain a symbolic expression for the elongation of the bar AC, δAC, in terms of H, W, E0, A0 (with E0 as E_0 and A0 as A_0):

δAC=

unanswered
You have used 0 of 3 submissions
Q1_2_4 : 80.0 POINTS
Now assume that the bar BC is a composite bar obtained by bonding two cables: a steel cable with cross sectional area AS=1000 mm2, and an aluminum cable with cross sectional area AA, as shown in the figure, so that the total cross sectional area of the bar BC is AS+AA. Take the Young's modulus of steel to be ES=200 GPa, and the Young's modulus of aluminum to be EA=80 GPa.
If the failure stress of aluminum σA,fail=500 MPa, and we want a safety factor SF = 2 against failure, obtain the value (in mm2), of the minimum cross sectional area AA,min of aluminum that you should have for the composite bar BC.

AA,min=

mm²
unanswered

Answer 1

Anyone please?

Answer 2

Any help please?

Answer 3

Anyone?

Answer 4

1. rho*g*A
2, 0.5*rho*g*A
3. 3/4*rho*g*A*L

Answer 5

3/4*rho*g*A*L is not good answer

Answer 6

Trustee thanks the first two answers right but third one is wrong, can you check please?

Answer 7

q1_2_1 400, 300, 700, 565.685
q1_2_2 -800, -300, 0, 700

Answer 8

Thanks simonsay,
in q1_2_1: 300 is wrong for me, is there maybe a -300?

Answer 9

q1-2 wrong

Answer 10

In my case it was 500 guys, just try it.

Answer 11

These are my results (done by me):
Q1_1_1
rho*g*A
3/2*rho*g*A

Q1_2_1
400
500
700
565.685424

Q1_2_2
-800
-300
0
700

Q1_2_3
((W*1.25)*(5/3*H))/(A_0*E_0)

need the rest...

Answer 12

Q1_2_4= 300 mm^2

Answer 13

Anyone for the rest please?

Answer 14

Sorry, just noticed Q1_1_1: 3/2*rho*g*A is WRONG!

It is 0.5*rho*g*A as trustee says.

Answer 15

Use the force method for statically indeterminate structures to obtain a symbolic expression for the reaction RCx at the support C in terms of ρ, g, A, L (with ρ written as rho):
RCx=
incorrect
34⋅ρ⋅g⋅A⋅L
You have used 1 of 3 submissions
Q1_1_3 : 40.0 POINTS

Obtain a symbolic expression for the axial force in the bar N(x) in terms of ρ, g, A, L, x (with ρ written as rho):
for 0≤x<L, N(x)=
unanswered
for L<x≤3L, N(x)=
unanswered
You have used 0 of 3 submissions
Q1_1_4 : 80.0 POINTS

Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written as rho). (Note: enter the expressions for the stresses with their appropriate signs.)
σmax,Tn=
unanswered
at location xmax,T=
unanswered
σmax,Cn=
unanswered
at location xmax,C=
unanswered
You have used 0 of 3 submissions
Q1_1_5 : 60.0 POINTS

Obtain a symbolic expression for the displacement ux(x=2L) in terms of ρ, g, E, L (with ρ written as rho):
ux(x=2L)=
unanswered
You have used 0 of 3 submissions

Answer 16

Q1_1_2. My answer is -4*rho*A*g*L

Answer 17

No it is not good Jason

Answer 18

Q.1_1_1
rho*g*A
1/2*rho*g*A

Q.1_1_2
-2*rho*g*A*L

Answer 19

Q11 2 always false

Answer 20

Q1_1_3

0<x<L
rho*g*A*(L-x)

L<x<3L
(rho*g*A)/2*(L-x)

Answer 21

Help with Question 1_1_2, 1-1-4, 1-1-5?
SERIOUS ANSWERS NEEDED
Use the force method for statically indeterminate structures to obtain a symbolic expression for the reaction RCx at the support C in terms of ρ, g, A, L (with ρ written as rho):

Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written as rho). (Note: enter the expressions for the stresses with their appropriate signs.)
σmax,Tn=
unanswered
at location xmax,T=
unanswered
σmax,Cn=
unanswered
at location xmax,C=
unanswered


Obtain a symbolic expression for the displacement ux(x=2L) in terms of ρ, g, E, L (with ρ written as rho):
ux(x=2L)=
unanswered

Answer 22

Please post the answers for 1_4 and 1_5

Answer 23

1_2 also

Answer 24

UX(=2l)
(3*g*L^2*rho)/(8*E)

Answer 25

Thanks dog

Answer 26

Great dog

Answer 27

1-1-2, 1-1-4

Answer 28

Q1_1_2 : 100.0 POINTS

Use the force method for statically indeterminate structures to obtain a symbolic expression for the reaction RCx at the support C in terms of ρ, g, A, L (with ρ written as rho):

Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written as rho). (Note: enter the expressions for the stresses with their appropriate signs.)

Answer 29

1_1_2
-A*g*L*rho

Answer 30

1000 bone cookies dog

Answer 31

1-1-4

Answer 32

Q1_1_4 : 80.0 POINTS

Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written as rho). (Note: enter the expressions for the stresses with their appropriate signs.)
σmax,Tn=
unanswered
at location xmax,T=
unanswered
σmax,Cn=
unanswered
at location xmax,C=
unanswered

Answer 33

Q1_1_4
I only have the locations
T=0
C= 3*L

Answer 34

I need Tn and Cn

Answer 35

I need all four parts for 1-1-4

Answer 36

Obtain symbolic expressions for the maximum tensile and compressive stresses ( σmax,Tn and σmax,Cn )and their locations (coordinates xmax,T and xmax,C ) in terms of ρ, g, L (with ρ written as rho). (Note: enter the expressions for the stresses with their appropriate signs.)
σmax,Tn=
unanswered
at location xmax,T=
unanswered
σmax,Cn=
unanswered
at location xmax,C=
unanswered

Answer 37

Please post 1_4 all parts

Answer 38

σmax,Tn= g*L*rho

at location xmax,T= 0

σmax,Cn= -g*L*rho

at location xmax,C= 3*L

my contribution :D have a nice day

Answer 39

Q1_2 _1
400
500
699.99
665.68

Answer 40

Q1_2_3 (25/12*W*H)/A_0*E_0

Answer 41

All you guys are awesome !! Thanks a billion !! :D

Answer 42

can anyone post the solutions pls!!