MATERIALS - A LEVEL PHYSICS
Hooke’s Law: States that the force applied to an object and the extension of the object are
directly proportional to each other while the environment conditions are constant, up to the
limit of proportionality.
- Shown by the straight line (showing the direct proportionality) passing through the
origin in a force-extension graph
- P = Limit the proportionality: The point after which Hooke’s Law is no longer
obeyed because extension is no longer proportional to the force applied.
- E = Elastic limit: A point somewhere after the limit of proportionality and if you
increased the force applied on the object beyond this, the material will deform
plastically (permanently stretched, or when load is removed, the material does not
return to its original shape / length)
● Elastic material: When an object returns to its original shape / length upon
the force applied on the object being removed.
● Elastic deformation: When an object can be temporarily stretched or
compressed by putting the object in tension or compression and it will return
to its original shape / length when the force applied is removed.
● Plastic deformation: When the force applied on the object is removed, the
object no longer returns to its original shape / length. Permanent deformation.
Tensile (“under tension”) stress: Force applied per unit cross sectional area
Stress (Pa) = Force (N) / cross-sectional area (m^2)
- Stress numbers are usually very large because cross-sectional area is usually very
small, resulting in the stress to be very large.
- Usually dealing with mega/giga/terapascals
Tensile (“under tension”) strain: Caused by tensile stress, and is defined as the extension
over the original length. Ratio of the extension of the material to the natural length.
Strain (no units) = Extension (m) / Original length (m)
When work is done on a material to stretch or compression, the energy is stored as elastic
strain energy.
Elastic strain energy (J) = ½ x Force (N) x extension (m)
Hooke’s Law: States that the force applied to an object and the extension of the object are
directly proportional to each other while the environment conditions are constant, up to the
limit of proportionality.
- Shown by the straight line (showing the direct proportionality) passing through the
origin in a force-extension graph
- P = Limit the proportionality: The point after which Hooke’s Law is no longer
obeyed because extension is no longer proportional to the force applied.
- E = Elastic limit: A point somewhere after the limit of proportionality and if you
increased the force applied on the object beyond this, the material will deform
plastically (permanently stretched, or when load is removed, the material does not
return to its original shape / length)
● Elastic material: When an object returns to its original shape / length upon
the force applied on the object being removed.
● Elastic deformation: When an object can be temporarily stretched or
compressed by putting the object in tension or compression and it will return
to its original shape / length when the force applied is removed.
● Plastic deformation: When the force applied on the object is removed, the
object no longer returns to its original shape / length. Permanent deformation.
Tensile (“under tension”) stress: Force applied per unit cross sectional area
Stress (Pa) = Force (N) / cross-sectional area (m^2)
- Stress numbers are usually very large because cross-sectional area is usually very
small, resulting in the stress to be very large.
- Usually dealing with mega/giga/terapascals
Tensile (“under tension”) strain: Caused by tensile stress, and is defined as the extension
over the original length. Ratio of the extension of the material to the natural length.
Strain (no units) = Extension (m) / Original length (m)
When work is done on a material to stretch or compression, the energy is stored as elastic
strain energy.
Elastic strain energy (J) = ½ x Force (N) x extension (m)
