Unit 2 Review - cusd80.com

Joint A
Fab

A Fac

25 lb 100 lb
50 lb
Joint
Fab B

Fbc Joint C
Fac

C 50 lb
75 lb
tB

Fbc

Steps for findin

1. Solve for Reaction force

a. Draw a FBD of the entir

b.  FX = 0;  FY = 0;  M

c. Use the above equation

2. FBD of each joint (use

3.  FX = 0;  FY = 0 at eac

4. Solve for forces
5. Draw final FBD

ng Truss Forces

es

re system

M=0

ns to solve for reaction forces

vector properties)
ch joint

Joint A FIND q F

Fab Joint A

A Fac
A

25 lb 2

Find q:
Tan q = O/A
Tan q = 5/2
q = 68.2 deg

For B

Fab 5

q Fac
2

25 lb

Joint A Redraw J

Fab In X and

Compon

A Fac

25 lb

A

Joint
Y
nents

Fab Y = F sin q = F sin 68.2
Fab X = F Cos q = F cos 68.2
Fac

25 lb

Joint A Sum Forc

Fab and Y dir

A Sum

25 lb Fac F sin

Sum forces in x = 0 0.93
Fcos 68.2 + F ac = 0 Fab
-26.9 * cos 68.2 = -Fac Fab
-10 = -Fac
Fac = 10 lb in tension F

A

ces in X
rections

m forces in y = 0
n 68.2 + 25 lb = 0
3 F = -25 lb
= -26.9 lb
= 26.9 lb in compression

Fab Y = F sin q = F sin 68.2

Fab X = F Cos q = F cos 68.2
Fac

25 lb

FIND q F
B Joint C

5 q
4 Joint C

Find q:
Tan q = O/A
Tan q = 5/4
q = 51.3 deg

For

Redraw Joint
In X and Y
Components

Fbc Y = F sin
Fbc X = F cos q = F cos 51.3

Fac = 10 lbs 50 lb

75 lb

Fbc Joint C
Fac

C 50 lb
75 lb
n q = F sin 51.3

b

Sum Forces in X
and Y directions

Sum forces in x = 0
-50 lb – 10 lb - Fcos 51.3 = 0
-60 lb = .625Fbc
-96 = Fbc
Fbc = 96 lb in compression

Fbc Y = F sin

Fbc X = F cos q = F cos 51.3

Fac = 10 lbs 50 lb

75 lb

Fbc Joint C

Fac
C 50 lb

75 lb
n q = F sin 51.3

Sum forces in y = 0
F sin 51.3 + 75 lb = 0

b 0.78 F = -75 lb
Fbc = -96 lb
Fab = 96 lb in compression

Material P

Properties

What Are M

Materials: Substances ou
are made

Materials are consist of p
categorized by physical an

Elemen

Metals Nonmet

Materials?

ut of which all things

pure elements and are
nd chemical properties
nts
tals Metalloids

Material Compos

Metal Elements

Distinguishing Characte

Good conductors of h
hard, shiny, reflect lig
typically have one to

sition - Elements

eristics
heat and electricity,
ght, malleable, ductile,
three valence electrons

Material Compos

Nonmetal Elements
Distinguishing Characte
Most are gases at roo

Solids are dull, brittle,
electrons are tightly a
to one atom; poor con
electricity

sition - Elements

eristics
om temperature

, and powdery;
attracted and restricted
nductors of heat and

Material Compos

Metalloids

Distinguishing Characte

Possess both metallic
properties

sition - Elements

eristics
c and nonmetallic

Material Compositio
Mixt

Compounds: created w
elements are chemica

Most substances are co

Mixtures: Non-chemica
two or more substance

Elements within the mixture

on – Compounds and
tures
when two or more
ally combined

ompounds

al combination of any
es

retain their identity

Material Cla

Common material classifi

Metallic Materials
Ceramic Materials
Organic Materials
Polymeric Materials
Composite Materials

assification

ication categories:

Metallic M
Distinguishing Charact

Pure metal elements

(Not commonly found or u

Metal element compou

(Commonly used due to the
properties of the compoun

Thermal and electrical

Mechanical properties
strength and plasticity

Materials
teristics

used)

unds (alloy)

e engineered
nd)

conductors
include

Ceramic Materials

Distinguishing Charact

Compounds consisting
nonmetal elements

Thermal and electrical

Mechanical properties
strength at high tempe
brittleness

teristics

of metal and

insulators
include high
eratures and

Organic Materials

Distinguishing Charact

Are or were once living

Consist of mostly carbo
hydrogen

Genetically alterable

Renewable

Sustainable

teristics

organisms

on and

Polymeric Materials

Distinguishing Charact

Compounds consist of m
organic elements

Low density

Mechanical properties i
flexibility and elasticity

Polymeric Subgroups

Plastics

Elastomers

teristics

mostly

include

Composite

Distinguishing Charact

Composed of more then
Designed to obtain desi
each individual materia

e Materials

teristics

n one material
irable properties from
al

Material

Refined material selectio

Mechanica
Physical
Thermal
Electroma
Chemical

Should also include rec
when choosing approp
a design

Selection

on based upon:
al

agnetic

cyclability and cost
priate materials for

Material

Mechanical Properties
Deformation and fractu
applied mechanical forc

Strength

Hardness

Ductility

Stiffness

Selection

ure as a response to
ces

Material

Thermal Properties
Affected by heat fluxes
changes

Thermal Capacity – Heat
material

Thermal Conductivity – C
transport heat

Thermal Expansion – Ho
contracts if the tempera

Selection

s and temperature

t storage capacity of a
Capacity of a material to

ow a material expands or
ature is raised or lowered

Material

Electrical Properties
Material response to el

Electrical Conductivity –
semiconductors, semim
superconductors

Thermoelectric – Electri
thermo responses; therm
electrical responses

Selection

lectromagnetic fields

– Insulators, dielectrics,
metals, conductors,

ical stimuli provoke
mo stimuli provoke

Material

Chemical Properties
Response and impact o
material structures

Oxidation and Reductio
and combustion

Toxicity – The damaging
on other materials

Flammability – The abil
ignite and combust

Selection

of environment on

on – Occur in corrosion
g effect a material has
lity of a material to