KPE 160H1-Module 1: Mechanics, Kinematics, and Kinetics – Vocabulary

Vocabulary flashcards covering key terms and their definitions from the lecture notes on mechanics, kinematics, kinetics, deformation, and related physical concepts.

Interval scale

A formal measurement scale used for physical phenomena, known as an interval scale.

Seven base quantities

The seven fundamental quantities with units derived from universal constants: Mass, Length, Time, Current, Temperature, Amount of substance (Mol), Luminous intensity (Light).

Mass

A base quantity representing how much matter is in a material body.

Length

The extent of space in one dimension; a base quantity.

Time

A fundamental quantity, a monotonically increasing quantity related to entropy.

Current

A base quantity representing the flow of electric charge.

Temperature

A base quantity describing thermal state.

Amount of substance (Mol)

A base quantity counting particles via a fixed number (Avogadro’s constant).

Luminous intensity (Light)

A base quantity describing the perceived power of light.

Mechanics

The branch that uses space, time, and matter to describe motion and forces.

Space

The unlimited 3‑dimensional realm in which all objects exist and events occur.

Distance

The linear measure of space; a scalar quantity.

Angle

A measure based on the arc subtended by a circle and the radius; measured in radians.

Radian

A unit for angle defined as the ratio of arc length to radius (L/r); essentially a dimensionless number labeled as radians.

2D/3D measures

Length (1D), Area (2D), Volume (3D) representing spatial extents.

Volume

The space occupied by a body in 3 dimensions.

Density

Density = Mass / Volume (M/V).

Location

Where an object is in space.

Orientation

The direction an object is facing in space.

Frame of reference

A coordinate system used to describe position in space (Cartesian coordinates).

Origin

The starting point of a coordinate system.

Axes

The linear scales used to measure each spatial dimension.

Center of mass (CoM)

The unique point from which the relative distances of all mass points balance to zero.

Center of gravity (CoG)

The balance point around which the weight of an object is balanced.

θx, θy, θz

Angles of rotation around the x, y, and z axes; rotations in the corresponding planes.

Motion

Change in position over an interval of time.

Linear motion

Change in location along a straight line over time.

Angular motion

Change in orientation with or without change in location.

Rotation

Angular motion about an axis; no change in CoG location.

Curvilinear motion

Motion along a curved trajectory.

Distance vs displacement

Distance is a scalar measure of path length; displacement is a vector measure of change in position.

Scalar

A quantity with only magnitude.

Vector

A quantity with magnitude and direction.

Linear distance

The measure of length along a path; distance travelled.

Linear displacement

Change in location; a vector.

Angular distance

Measure of angle between two lines, planes, or frames.

Angular displacement

Change in orientation.

Speed

Scalar measure of the rate of change of position.

Linear speed

Scalar rate of change of location; often denoted S.

Velocity

Vector measure of the rate of change of position; includes magnitude and direction.

Linear velocity

Vector rate of change of location.

Angular speed

Scalar rate of change of orientation.

Angular velocity

Vector measure of the rate of change of orientation.

Acceleration

Rate of change of velocity; a vector quantity.

Linear acceleration

Rate of change of linear velocity; direction follows velocity.

Angular acceleration

Rate of change of angular velocity.

Impulse

Impulse = force × duration of force.

Work

Energy transfer between bodies; measured in Joules.

Power

Rate of work; measured in Watts.

Gravity

The downward force toward Earth’s center; g ≈ 9.81 m/s².

Weight

The force of gravity acting on a body.

Inertia

Mass property resisting changes in motion.

Momentum

Inertia × velocity (linear momentum).

Kinetic energy

½ × Mass × Velocity² (linear form).

Newton's first law

An inertial body maintains constant velocity unless acted on by a net external force.

Newton's second law

Net force causes acceleration proportional to net force and inverse to inertia.

Newton's third law

For every action, there is an equal and opposite reaction.

Adhesion

Forces between contacting bodies resisting separation under tensile loads.

Friction

Resistance to motion that dissipates energy.

External friction

Friction between objects in contact.

Sliding friction

Friction for objects sliding over one another.

Rolling resistance

Friction for wheels rolling over a surface.

Fluid drag

Friction for objects moving through fluids.

Internal friction

Friction during deformation inside a material.

Rotational inertia

Resistance to angular acceleration depending on mass and its distribution relative to the rotation axis.

Moment of a force

A measure of tendency to cause rotation; magnitude = force × moment arm.

Moment arm

Perpendicular distance from the force line to the center of rotation.

Fulcrum

The pivot point for a lever.

Lever leverage

The moment arm of a muscle acting at a joint.

Deformation

Change in shape of a body or figure.

Elastic deformation

Reversible deformation that stores elastic potential energy.

Elasticity

Property of solids allowing energy storage through deformation.

Hooke's law

F = kx for linear deformation; governs linear elasticity.

Stiffness

Resistance to deformation; ideal rigid bodies have infinite stiffness.

Elastic limit

End point of the elastic range; beyond it, plastic deformation begins.

Plastic deformation

Irreversible deformation that dissipates energy.

Yield point

Point at which elastic deformation ends and plastic deformation begins.

Fracture

Engineering term for failure; clinicians may term it as strain, sprain, tear, or rupture.

Ductile vs brittle

Ductile/malleable materials have large plastic ranges; brittle materials have small plastic ranges.

Viscosity

Internal resistance to flow; dissipates energy; proportional to deformation velocity.

Visco-elastic

Materials that are elastic and viscous; deformation rate depends on viscosity.

Half-life of deformation

Time required to reach halfway between current and final shape during deformation.

Energy storage/transfer/dissipation

Energy can be stored (gravity, inertia, elasticity), transferred (forces, contacts), or dissipated (friction).

Rigid body

An ideal body with infinite stiffness, resisting deformation.

Plane of rotation

Axis perpendicular to the plane in which a shape exists; often the z-axis is used.