Forces can deform objects or change their motion, and structures resist forces to prevent breaking or excessive deformation. Structures are natural or artificial and must be stable, resistant, and rigid. Stability depends on center of gravity and base. Resistance depends on material, quantity, and shape. Rigidity comes from rigid joints, triangles, and cross-bracing. Loads apply stresses like tension, compression, bending, torsion, and shear. Structures serve their purpose if stable, resistant, and rigid.

1. structures

2. FORCES
A force is anything that
can deform a body or
change its state of rest
or movement.
But if a classmate
hold it, another
force counteracts
your force and
prevents the book
from moving.
If you drop your rubber
and your pencil so that
they hit each other, the
direction of their
movements change
When you
press down
your rubber, the
force you apply
causes its
shape to
change
When you push
your book, the force
you apply causes
the book to move

3. STRUCTURES
A structure is a set
of elements in a body
that are intented to resist
the effects of the forces
that act on it.
A structure prevents a body
from breaking or becoming
too deformed

4. TYPES OF STRUCTURES
A structure is a set
of elements in a body
that are intented to resist
the effects of the forces
that act on it.
Natural structures
are the ones
created by nature
A structure prevents a body
from breaking or becoming
too deformed
Artificial
structures are the
human-made ones.

5. LOADS
A LOAD is the force that
acts on a structure.
The force of the wind acts on the
tree´s branches
The weight of the cars
acts on the bridge
The weight of the man
acts on the armchair
The weight of the
backpack acts on
the boy´s skeleton

6. STRESSES
STRESSES are the
effects that loads cause
in a structure.
Living things feel this
effect
It can be very slight
or, if it strong, it can
even hurt us
Objects do not have
feelings, but forces
act on them in a
similar way and
produce or try to
produce
deformations. In both cases this
internal tension is called
stress.

7. TYPES OF STRESSES
TRACTION
Load tends to
stretch the
structure.
COMPRESSIO
N
Load tends to
flatten or
compress the
structure.
BENDING
Load tends to
bend the
structure.
TORSION Load tends to
twist the
structure.
SHEAR Load tends to
shear the
structure.

8. TYPES OF STRESSES
TRACTIO
N COMPRESSIO
N
BENDING
TORSIO
N
SHEAR
The pendan stretches the
necklace
The weight of the
branches
compresses the tree
trunk
The weight of
the girl bends
the rod
The cloth is
twisted when we
turn it ends in
opposite
directions.
Shear comes from
the force the jacket´s
weight exert and the
opposition resistance
of the hanger to it

9. STRUCTURAL CONDITIONS
STABILITY
The capacity of a
structure to remain
upright and not
tip over.
RESISTANCE
The capacity of a
structure to bear
the stresses
without breaking.
RIGIDITY
The capacity of a
structure to
become
deformed, but the
deformation must
not prevent it from
fulfilling its
function.
1 2 3
The conditions for a structure to work well are:
For a structure to serve its purpose, it must be stable, resintant and rigid

10. STRUCTURAL CONDITIONS
STABILITY
Stability is the
capacity of a
structure to remain
upright and not
tip over.
The stability depends on:
The centre of gravity of the
object.
The way the object stands
on the ground
The centre of gravity of a body is a point
where all its mass is concentrated.
Its centre of gravity
vertical projection stands
inside its base, so that
the car will remain upright
Its centre of gravity
stands outside its
base, so that the car
will tip over
Centre of
gravity
The closer to the ground the
centre of gravity of a body is, the
more
stable the structure is.
Centre
of
gravity

11. STRUCTURAL CONDITIONS
STABILITY
Stability is the
capacity of a
structure to remain
upright and not
tip over.
We can give a structure stability by:
Adding mass to its base
Bracing it
Burying its bottom section
underground

12. STRUCTURAL CONDITIONS
Resistance depends on:
The material used to build the
structure
The quantity of material used
The shape of the structure
RESISTANCE
The capacity of a
structure to bear
the stresses
without breaking.
It will break
It will break
It will break

13. STRUCTURAL CONDITIONS
Rigidity comes from:
Making rigid joints
Using triangular
structures
It can be easily
deformed
RIGIDITY
The capacity of a
structure to become
deformed, but the
deformation must not
prevent it from
fulfilling its function.
It can not be
deformed
Adding
gusset
plates, joints
become rigid
Adding cross bracing,
structures become rigid