test 4- Final Flashcards
stresses and strains on the body
internal and material properties of biological materials (compression, tension, bending, torsion, shear)
external forces that act on the body affect the movements of..
the entire boys and also impose loads that affect the internal structures
internal structures of the body
cartilage, tendons; ligaments, bones, and muscle
understanding of the mechanical properties of the internal structures is important for…
preventing injury and evaluating the causes of injury
stress
the external forces that act on the body are resisted by internal forces and cause deformation of the body
the amount of deformation produced is related to…
the stress caused by the forces and the material that is loaded
Do the 2 rubber bands stretch as much as the single rubber band did under the same force?
the deformation (or stretch) of the 2 rubber bands was not as large as that of the single rubber band unless you exerted twice as much force (the stress of the 1 rubber band is 2x as large as the stress of the 2 rubber bands)
mechanical stress
the internal force divided by the cross-sectional area of the surface on which internal force acts (stress may vary within an object and is associated with a specific internal surface)
three principal stresses
tension, compression, shear
SI Unit for Stress
N/m^2 (Pascals)
static equilibrium
if the rubber band is held still in a stretched position; ignoring weight, the pulling force at each end must be equal
the force of stress represents…
the resultant of all the individual intermolecular bond forces that act across the surface of the imaginary cut and hold the rubber band together
the cross sectional area (stress)
is at the imaginary cut plane (analysis plane) used to define the stress at this plane
stress=
internal force/CSA of the internal surface
E=
change in length/ original length
axial stresses (normal or longitudinal stresses)
tension and compression; acts perpendicular (or normal) to the analysis plane
transverse stress
shear
Tensile Stress
(rubber band example) is the axial or normal stress that occurs at the analysis plane as a result of a force or load that tends to pull apart the molecules bonding the object together at that plane
which anatomical structures are longer in one dimension than in the other 2? (tension)
long bones, muscles, tendons, ligaments
stress in such structures is typically analyzed by (tension)
considering analysis planes that cut through the structure perpendicular to its longest dimension
the stresses that act perpendicular to the analysis planes (this the long acid of the structure are called
axial, normal, or longitudinal stresses
axial loading (tension)
a loading situation in which the forces act in the direction of the long axis of the bone (if cut perpendicular stress could be determined in the bone)
if the force tends to pull the bone apart and stress acts away from the analysis plane the stress is…
tensile stress
if the cross sectional area changes as you move distally along its length what else changes?
the stress changes/varies (inversely)
an object tends to deform by stretching or elongating in the direction of the…
external loads
for most materials, this elongation is directly proportional to the…
magnitude of the stress
in humans, very large tensile loads may…
sprain or rupture ligaments and tendons, tear muscles and cartilage, and fracture bones
