chapter four Flashcards
force
something that possesses the capability to cause a change in motion of a system
motion
change in position with respect to both spatial & temporal frames of reference
Newton’s first law: Law of Inertia
the current state of rest or motion of the system will be maintained unless and until there is interaction with an external force, no change of motion occurs without force
Newton’s second law: Fundamental Law of Dynamics or Law of Acceleration
change of motion is directly proportional to the magnitude of the applied force
acceleration
a change in the state of motion of the system caused by an applied force
Newton’s third law: Law of Reciprocal Actions or Law of Action-Reaction
forces exist in pairs
field force
a force that acts at a distance without making contact with the object that it is affecting
strong nuclear force
force that occurs between subatomic particles & prevents the nucleus of an atom from exploding because protons produce a repulsive electric force
electromagnetic force
force that occurs between electric charges
weak nuclear force
force that is a product of some radioactive decay processes
gravitational force
force that exists between bodies of mass
contact forces
forces that are the result of physical contact between two bodies
external forces
forces that interact with the system from the outside
internal forces
forces that act within the defined system
action force
the initially applied force
reaction force
the simultaneous equal counterforce actin gin the opposite direction to the action force
friction
the force that resists the sliding of two objects in contact
normal force
force that acts downward on one surface & upward on another
ground reaction force
an equal & oppositely directed normal force from Earth
static friction
friction that exists when two contacting surfaces are not currently sliding relative to each other but do possess the potential for movement
coefficient of friction
an experimentally measured dimensionless value representing the proportion of friction force resisting sliding motion of the object to the normal force holding the objects together (represents difficulty of sliding over another surface because of their textures)
impending motion
the moment immediately before an object begins to slide because of the application of a force
kinetic friction
friction that exists when two surfaces are already sliding relative to each other
rolling friction
friction that exists whenever one surface is rolling over another but is not sliding across it
pressure
the magnitude of applied force acting over a given area
tensile strength
the maximum stretch that a material can withstand without rupture
Pascal’s law
pressure applied to a fluid is transmitted undiminished to every point of a fluid and to the walls of the container
stress
the external force acting to deform a material
strain
the resulting magnitude of deformation as a result of an applied stress
poisson’s ratio
an expression of the tendency of a material to exhibit transverse (lateral) strain simultaneously with axial (longitudinal) strain
elastic modulus
an expression of the relationship of stress & strain for a given material and type of deformation
tension stress
occurs when two forces are applied to a system in opposite directions away from each other
compression stress
the result of two forces being applied to the system in opposite directions toward each other
shear stress
occurs from application of two parallel forces that tend to simultaneously displace one part of a system in a direction opposite another part of the system
bending
occurs when two off-axis forces are applied such that tension stress is caused on one side of the system & compression stress occurs on the other side
torsion
caused by two forces being applied in such a way that part of the system is rotated around its longitudinal axis in a direction opposite of the rotation of another part of the system
Young’s modulus
term for the elastic modulus specifically referring to a condition of tension stress
elastic region
the linear portion of any given stress-strain curve; a material will return to its original shape if tensile stress is removed within this range
yield point
the point at which an applied stress can lead to permanent deformation
plastic region
the nonlinear response of the material after the yield point; some degree of deformation will persist after removal of the stress
strength
the maximum stress or strain that a material can withstand without permanent deformation
ductility
the force per unit area required to deform a material and is represented by the steepness (slope) of the stress-strain curve
toughness
total energy required to cause material failure
yield strength
stress at the yield point of a material
ultimate strength
the maximal stress that a material can withstand before failing
failure strength
the stress at which a material actually breaks or ruptures
ductile
the quality of material that fails at low stress but can withstand a large strain; also known as pliant
brittle
the quality of a material that can withstand high stress but fails with relatively low strain; also known as stiff
coefficient of restitution
a parameter observed after reformation that indicates the ability of an object to return to its original shape after deformation; also known as coefficient of elasticity
viscoelastic
quality of a material whose deformation is affected by both the rate of loading and the length of time that it is subjected to a constant load
creep
property of experiencing increasing strain (continued deformation) under a constant stress
stress relaxation
the eventual decrease in stress that will occur as fluid is no longer exuded
buoyant force
the vertical, upward-directed force acting on an object that is submerged in a fluid
Archimedes’ principle
a body submerged in a fluid will be buoyed up by a force that is equal in magnitude to the weight of the displaced water
dynamic fluid force
the equal and oppositely directed force of the fluid particles in reaction to the applied force of the system moving through the fluid
drag force
the parallel component of dynamic fluid force that acts in the opposite direction of system motion with respect to the fluid; tends to resist motion of the system through the fluid
lift force
the perpendicular component of dynamic fluid force can act in any direction that is perpendicular to system motion with respect to the fluid; tends to change the direction of system motion through the fluid
motive force
a force that tends to cause a change in motion in the form of increased velocity or change in direction of the system; also known as propulsive force
resistive force
a force that tends to prevent changes in motion by other external forces or decrease the velocity of a system that is already in motion
centripetal force
any force that causes a system to exhibit circular motion
maximal oxygen uptake
maximal capability to use oxygen in metabolic processes to make ATP; expresses as VO2 max
hoop stress
stress caused by compressive forces applied to intervertebral discs
radial expansion
the bulging of an intervertebral disc in accordance with Poisson’s ratio
