University Physics Volume 1

# Key Terms

### Key Terms

breaking stress (ultimate stress)
value of stress at the fracture point
bulk modulus
elastic modulus for the bulk stress
bulk strain
(or volume strain) strain under the bulk stress, given as fractional change in volume
bulk stress
(or volume stress) stress caused by compressive forces, in all directions
center of gravity
point where the weight vector is attached
compressibility
reciprocal of the bulk modulus
compressive strain
strain that occurs when forces are contracting an object, causing its shortening
compressive stress
stress caused by compressive forces, only in one direction
elastic
object that comes back to its original size and shape when the load is no longer present
elastic limit
stress value beyond which material no longer behaves elastically and becomes permanently deformed
elastic modulus
proportionality constant in linear relation between stress and strain, in SI pascals
equilibrium
body is in equilibrium when its linear and angular accelerations are both zero relative to an inertial frame of reference
first equilibrium condition
expresses translational equilibrium; all external forces acting on the body balance out and their vector sum is zero
gravitational torque
torque on the body caused by its weight; it occurs when the center of gravity of the body is not located on the axis of rotation
linearity limit (proportionality limit)
largest stress value beyond which stress is no longer proportional to strain
normal pressure
pressure of one atmosphere, serves as a reference level for pressure
pascal (Pa)
SI unit of stress, SI unit of pressure
plastic behavior
material deforms irreversibly, does not go back to its original shape and size when load is removed and stress vanishes
pressure
force pressing in normal direction on a surface per the surface area, the bulk stress in fluids
second equilibrium condition
expresses rotational equilibrium; all torques due to external forces acting on the body balance out and their vector sum is zero
shear modulus
elastic modulus for shear stress
shear strain
strain caused by shear stress
shear stress
stress caused by shearing forces
static equilibrium
body is in static equilibrium when it is at rest in our selected inertial frame of reference
strain
dimensionless quantity that gives the amount of deformation of an object or medium under stress
stress
quantity that contains information about the magnitude of force causing deformation, defined as force per unit area
stress-strain diagram
graph showing the relationship between stress and strain, characteristic of a material
tensile strain
strain under tensile stress, given as fractional change in length, which occurs when forces are stretching an object, causing its elongation
tensile stress
stress caused by tensile forces, only in one direction, which occurs when forces are stretching an object, causing its elongation
Young’s modulus
elastic modulus for tensile or compressive stress