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1º ESO. STRUCTURES

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Moisés Llorente Santos

on 9 April 2015

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Transcript of 1º ESO. STRUCTURES

1. FORCES AND STRUCTURES
What is a force?

UNIT 5: STRUCTURES (pages 90 - 100)
Moisés Llorente
Colegio Madrigal (Fuenlabrada)

A force is anything that can deform a body (static effect) or change its state of movement or rest (dynamic effect)
How many different types of forces are there in the nature?
force of the wind
mechanical forces that move machines
pressures of gases and liquids in closed containers
our own muscles
1.2 STRUCTURES (page 90)
What's a structure?
A structure is the set of elements in a body that are intended to resist the effects of the forces that act on it.
Which fall faster, a feather or a heavy bowling ball?
Examples of structures
bridge
house skeleton
stork's nest
electrical tower
LOADS (page 90)
The forces that act on a structure are called
loads
.
How many types of loads are there?

Look for in the book and copy them in the notebook (page 90).
Draw in your notebook the loads acting on each structure:
A car crossing a suspension bridge
An electric cable hanging on an electrical tower.
STRESSES (page 92)
We call a stress to the internal tension of a material, caused by one or more external forces acting on it.
Stresses can deform the materials.
Main types of stresses:
1. Traction
2. Bending
Main types of stresses:
3. Compression
4. Torsion
Main types of stresses:
5. Shear or cutting
PUSH
PULL
MOTION
DEFORMATION
Tacoma Narrows bridge collapse
(1940)
CONTACT FORCES
NON-CONTACT FORCES
Gravity
Electromagnetic forces
NASA VACUUM CHAMBER
EXPERIMENT
VOLUNTARY RESEARCH WORK
TOPIC: The longest bridge in the world.
1. Name of the bridge.
2. Length.
3. Year of construction.
4. Main characteristics and brief history.
5. Add some pictures and/or videos.
You can present your work in a word, pdf or prezi, before March the 3th, obtaining
up to 1 extra point
in the next exam.
Send it to: practicasmoises@gmail.com
Draw this swing into yout notebook and then (using a pencil first), draw the diferent stresses acting on each part of it:
1
2
3
4
bending
compression
traction
compression
1- Take an old and used piece of paper, and roll it.

2- Listen to your teacher's instructions and do the appropriate action in each case.

STRESSES ACTIVITY (II)
STRESSES ACTIVITY (I)
STRUCTURAL CONDITIONS (page 94)
A well designed structure must be...
Stable
Resistant
Rigid
This definitions corresponds to... rigidity, stability or resistance?
: the capacity of a structure to bear tensions without breaking.
: the capacity of a structure to remain upright and not tip over.
: the capacity of a structure to fulfill its function after being slightly deformed when a force is applied to it.
Resistance
Stability
Rigidity
Triangulated structures
Triangulation is a technique used to design and build resistant, stable and rigid structures.
Triangles are the only polygons that doesn't get deformed when a force is applied on them.
Why triangles?
TRIANGULATION ACTIVITY
Copy the following structures in your notebook and complete them to get restistant and rigid structures, using triangulation.
Forces
Force
BOOK ACTIVITIES
Page 95 activities 12, 13, 17
THE IMPOSSIBLE BRIDGE: AN UNSUCCESFUL ATTEMPT TO JOIN AFRICA AND EUROPE
Full transcript