Elasticity
Things to learn
States of Matter
Hook’s low
Elasticity
Stress, Strain, Elastic Moduli
States of Matter
Solid
Have definite volume
Have definite shape
Molecules are held in specific locations by
electrical forces
vibrate about equilibrium positions
can be modeled as springs connecting
molecules
Liquid
• Has a definite volume
• No definite shape
• Exist at a higher temperature
than solids
• The molecules “wander” through
the liquid in a random fashionThe
intermolecular forces are not
strong enough to keep the
molecules in a fixed position
Gas
• Has no definite volume
• Has no definite shape
• Molecules are in constant random motion
• The molecules exert only weak forces on each other
• Average distance between molecules is large compared to the size of the
molecules
•An elastic material is one that
returns to its original shape after a
deformation.
•An inelastic (plastic) material is one
that does not return to its original
shape after a deformation.
Soccer Ball
Clay
An elastic collision loses no energy. The
deform-ation on collision is fully
restored.
In an inelastic collision, energy is lost
and the deformation may be
permanent.
A spring is an example of an elastic body that
can be deformed by stretching.
F
x
A restoring force, F,
acts in the direction
opposite the
displacement of the
oscillating body.
F = -kx
When a spring is stretched, there is a restoring
force that is proportional to the displacement.
F = -kx
F
k
x
x
F
•The spring constant k is a measure of the elasticity
of the spring.
•The spring constant k is a property of the spring