Work

is defined as the product of force and displacement in the direction of that force, representing how energy is transferred from one object to another.

Energy

the capacity to do work, indicating the potential to perform tasks or exert forces.

Kinetic Energy

Energy due to motion; a moving object can perform work due to its velocity. For example, a car moving at high speed has significant kinetic energy.

Potential Energy

Energy stored due to an object's position; for instance, a book on a shelf has gravitational potential energy due to its height above the ground.

Gravitational Energy

A specific type of potential energy that depends on an object's weight and its elevation relative to the Earth.

Power

The rate at which work is done, calculated as work divided by time. For example, a machine that does 100 Joules of work in 2 seconds has a power output of 50 Watts.

Positive Work

Occurs when a force causes displacement in the same direction, increasing energy in the system.

Negative Work

Happens when the force acts in the opposite direction of displacement, resulting in energy removal.

Relative Motion

The motion of an object as observed from another moving object or reference point, such as a passenger in a moving train observing another train.

Absolute Motion

The motion of an object measured against a fixed, stationary reference point, like a car moving on a road.

Buoyancy

The upward force experienced by an object immersed in a fluid, always acting vertically against gravity.

Pressure

Defined as force per unit area applied on a surface, crucial in understanding fluid behavior.

Lift Force

The component of fluid force acting perpendicular to the relative motion, essential in aerodynamics.

Bernoulli's Principle

States that faster-moving fluids produce less force laterally than do slower-moving fluids; fluids move faster over a curved surface than a flat surface

Magnus Effect

A phenomenon where someone/something enacts a spinning effect on an object moving through a fluid that experiences a force perpendicular to the direction of motion

Stress

The internal force per unit area within materials, which resists external forces; calculated as force divided by area.

Strain

The measure of deformation experienced by a material in response to stress, expressed as a ratio of change in length to original length.

Tensile Stress

The internal resistance to being "stretched" and it acts perpendicular to the cross-section of the tissue

Compressive Stress

The internal resistance to being "squashed" and it acts perpendicular to the surface but in the opposite direction

Shear Stress

The internal resistance to "sliding/slipping" forces and it acts parallel to the cross-section

Elastic Modulus

The ratio of stress to strain, indicating a material's stiffness; slope of the stress-strain curve with stiff material having less strain and pliant materials having more strain

Yield Strength

The stress level at which a material begins to deform plastically; important for determining safe load limits.

Ultimate Strength

The maximum stress a material can withstand before failure occurs.

Stiff

Materials that resist deformation; examples include metals like steel.

Ductile

Materials that can undergo significant deformation before breaking, such as copper and aluminum.

Brittle

Materials that fracture with little deformation, like glass or ceramics.

Pliant

Materials that are flexible and can be easily shaped without breaking, such as rubber.

Toughness

The ability of a material to absorb energy; tougher materials require more energy to break, such as certain plastics.

Viscosity

Measure of the internal friction between the layers of molecules of a fluid or the resistance of a fluid to shear forces.

Strain Energy

Energy due to deformation of an object; fiberglass pole bending during pole-vaulting

Drag Force

The component of the resultant dynamic fluid force that acts in opposition to the relative motion of the object with respect to the fluid

Fluid Force Factors

Velocity of object, surface area, shape of object, density, viscosity, surface texture

Tensile Strain

The resulting elongation or lengthening of the tissue or biological matter

Compressive Strain

The resulting shortening or "bulging" of the tissue

Shear Strain

The resulting change in the angle or orientation of the internal molecules

Bending Load

Tension and compression are produced at the analysis plane of 3 or more forces to create force couples at the opposite ends of the object

Torsion Load

Shear stress acting parallel to the analysis plane as a result of opposing torques applied about the long axis of the body

Elastic Behavior

Material deforms and returns to its original length when unloaded

Plastic Behavior

Material deforms but does not return to its original length; permanent deformation

Elastic Limit

The yield point for a material on the stress-strain curve; stress above this point causes permanent deformation of material

Combined Loading

Human bones under complex loading from gravity, tendons, ligaments, other bones, contact forces, etc

Mechanical Loading

When external forces are not uniaxial, more complex loading occurs - bending, torsion, combined

Specific Gravity

Ratio of the weight of the object to the weight of the same volume of water

Relative Velocity

Difference between the velocity of the object and the fluid

Surface Drag

Friction between the fluid molecules and the surface of the object; rough surfaces create larger friction forces

Form Drag

Impact forces between the molecules and the object; broad, flat leading surfaces of an object create larger impact force

Laminar Flow

A fluid motion that is smooth, parallel layers that slide past one another without mixing or creating turbulence; when molecules stay close to the surface

Turbulent Flow

A fluid regime characterized by chaotic, irregular motion featuring rapid, random fluctuations in velocity and pressure; when molecules separate from the surface

Viscoelasticity

The time-dependent mechanical behavior - how the relationship between stress and strain is not constant but depends on the time of displacement/load

Creep

Represents how quickly cartilage or material reaches a constant state of strain

Stress Relaxation

A feature of a ligament or tendon where the stress acting on it will eventually be reduced under a constant state of deformation

Poisson's Ratio

The width of an object also changes as it lengthens or shortens

Backspin

Occurs when the bottom of a ball rotates in the same direction as the ball moves through the air - greater perpendicular force upwards

Topspin

Upper surface has forward velocity relative to the center of the ball, and when the lower surface has backward velocity relative to the center of the ball - greater perpendicular force downwards

Archimedes Principle

An object submerged in a fluid experience an upward buoyant force equal to the weight of the fluid it displaces

Toe Region

The very first phase of the stress-strain curve for ligaments, tendons, and skin - collagen fibers are crimped/wavy in this phase and start to unfold