4th post

When a structure is stable?
we say that a structure is stable when it remains in equilibrium even when a force is applied to it

What is the centre of gravity?
the centre of gravity is thge point where the weight of an object is considered to be concentrated 

Machine
we use the word machine to describe a set of elements or parts that work together and use energy to perform a task and obtain a result.

Machine have 3 components:

Driver elements: feeds energy to the machine 

Driven element: receives the force produced in the machine

Converting and/or transmitting element: transmits and/or converts the motion from the driver element to the driven element .

Mechanisms
devices that transmit and/or convert motion are called mechanisms

Motion transmission mechanisms is fed energy from the driver element and simply transfers it to driven element 

Example : lever

Motion converssion mechanisms coverts tyhe movement of the driver element into a movement that the driven element can use

Example : cams

Lever
is a rigid bar that can pivot on a point support called a fulcrum

Puleys

Puleys are used to lift heavy loads.They are wheels with a grooved rim.

Belt and pulley system

This system is made up of two pulley wheels joined by abelt that solts into the grooved rim of the wheel.

Ex: 

Gears

A gear is a mechanism consisting of two wheels with teeth.

Ex : 


Taging Machine

3rd post

Stresses are the physical demands that a body or object must withstand when one or more external forces are applied to it

Basic stresses 

Compression is caused by forces acting on a body that tend to flatten it or reduce its lenght or thickness. It happens in strcutures that need to support weights. For example, when we lean on a table, it undergoes compressive stress, columns are also subject to compressive stress.

Tension is caused by forces acting on a body that tend to stretch it. for example, when two people pull on an object from opposite directions.

Bending is caused by forces acting on an element that make it curve or bend. it is done by supporting the two ends and applying force in the centre, as shown in the figure to the right. this is what happens to a shelf when we put losts of heavy books on it

Torsion is caused by forces acting on a body that make it twist. for example, when two people hold a towel at either end and twist it to wring it out, a crank is also subjectd to torsion

Shear is caused by two equal forces applied in oppsite directions that act on lines of action close to each other. Shear stress will tend to cut the material if it cannot twist or bend. For example, when we cut paper with a pair of scissors, or the point where a beam rests on a column.

 Ragidity
it does not change shape when force is applied to iy. By contrast, if the material does change shape, we say that is deformable

12. think about the following objects and state whether they are rigid, plastic or elastic: ballon, empty drinks can, window frame, clay, catapult, door.

ballon : plastic
empty drinks can : rigid
window frame : rigid
clay : elastic
catapult : rigid
door : rigid

2nd post

STRUCTURES

Def:

Is a collection of elements arranged in a optimum way to support a body or an object

                      PUENTE MONUMENTAL DE ARGANZUELA

-Mass Structures these are solid, heavy and very sturdy structures examples include walls, dams, etc.

-Frame Structures these structure are formed by columns and beams that acht a supporting elements. one example might be the structure of a building

-Truss Structure these structures are composed of bars that form triangles. they are lightweight and sturdy. example includes cranes, electricity pylons, etc

-Suspended Structures these are held in place by cables and suspenders attached to sturdy example includes suspensions bridges, tents, marquees, etc

Force is an influence that can be deform a body or change its movement, or produce motion in a body at rest

Stresses are the physical demands that a body or object must withstand when one or more external forces are applied to it

Presentation

hello! we are Ronald and Nerea from 2ºA and we are going to talk about structures