3 post:Stresses and rigidity

·Stresses: Are the physical demands that a body or object must withstand when one or more external force are appplied to it.

· Types of stresses:

·Compression: This is caused by forces acting on a body that tend of flatten it or reduce its length or thickness

·Tension(or Traction): This is caused by foces acting on a body that tend to stretch it.

·Bending: This is caused by forces acting on an element that make it curved or bend. It is done by supporting the two ends and applying force in the centre.

·Torsion: This is caused by forces acting on a body that make it twist.

·Shear: This is caused by two equal forces applied in opposite 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

·Ridigity: If a material is rigid, does not change shape when force is applied to it. By contrast, if the material does change shape, we say that it is deformable.

12. think about the following object and start whether they are rigid, plastic or elastic: ballon, empty drinks can, window frame, clay, catapult, door.
Rigid: Door, catapult.
Plastic: Window frame, empy drinks can.
Elastic: Clay, ballon.