Physics Vocabulary: Mechanics, Energy, Gravity, and Motion

Vocabulary practice flashcards covering Newton's laws of motion, momentum, gravity, rotational motion, and energy.

Momentum

A property of moving objects representing inertia in motion, calculated as mass multiplied by velocity ($p = m \times v$).

Impulse

The product of the force acting on an object and the time interval over which it acts ($J = F \times t$), which equals the resulting change in momentum.

Law of Conservation of Momentum

The law stating that in the absence of an external force, the total momentum of a system remains unchanged ($p_{\text{initial}} = p_{\text{final}}$).

Elastic Collision

A collision in which colliding objects rebound without lasting deformation or any generation of heat.

Inelastic Collision

A collision in which colliding objects suffer lasting deformation and/or generate heat.

Law of Universal Gravitation

The law stating that every body attracts every other body with a force directly proportional to the product of their masses and inversely proportional to the square of the distance separating their centers ($F \cong \frac{m_1 m_2}{d^2}$).

Universal Gravitational Constant ($G$)

The fundamental constant linking force with mass and distance in Newton's law of gravitation, equal to $6.67 \times 10^{-11}\,N\,m^2\,kg^{-2}$.

Inverse-Square Law

A relationship where a physical force or intensity decreases inversely with the square of the distance from its source ($\text{Gravitational force} \propto \frac{1}{d^2}$).

Weight

The force an object exerts against a supporting surface.

Weightlessness

A state experienced by an object in free fall when there is no normal or support force acting upon it.

Rotation

Circular motion that occurs when an object turns about an internal axis passing through the object itself.

Tangential Speed

The linear speed of a point on a rotating body along its circular path, calculated as radial distance multiplied by rotational speed ($v = r \omega$).

Rotational Speed

The number of rotations or revolutions per unit of time (denoted as $\omega$), which is constant for all points on a rigid rotating body.

Rotational Inertia

The property of an object to resist changes in its rotational state of motion, depending on the object's mass, the mass distribution around the rotational axis, and the position of the axis.

Torque

An influence or twisting force that alters the rotational speed of an object, calculated as lever arm multiplied by force ($\tau = r F$).

Lever Arm

The perpendicular distance from the axis of rotation to the line of action of the applied force.

Center of Mass

The average position of all the mass that constitutes an object.

Center of Gravity

The average position of weight distribution for an object, key to stability when a vertical line drawn downward from it remains inside the base of support.

Centripetal Force

A center-directed force that pulls an object into a curved or circular motion path, expressed as $F_{\text{centripetal}} = \frac{m \times v^2}{r}$.

Centrifugal Force

An apparent outward force experienced by an occupant inside a rotating reference frame, caused by inertia rather than a true external interaction.

Angular Momentum

The rotational inertia of an object multiplied by its angular velocity ($L = I \times \omega$), or $L = m \times v \times r$ for a point-like mass.

Law of Conservation of Angular Momentum

The law stating that if no net external torque acts on a rotating system, the total angular momentum of that system remains constant.

Energy

A property of a system that enables it to do work or supply heat.

Work

The product of the net force exerted on an object and the distance through which it moves ($W = F d$), measured in joules ($1\,J = 1\,N \cdot m$).

Power

The rate at which work is done ($P = \frac{W}{t}$), measured in watts ($1\,W = 1\,J/s$).

Gravitational Potential Energy

Stored energy held in readiness due to an object's elevated position, calculated as weight multiplied by height ($PE = m \cdot g \cdot h$).

Kinetic Energy

The energy an object possesses because of its motion, equal to half its mass times the square of its speed ($KE = \frac{1}{2} m v^2$).

Work-Energy Theorem

The principle stating that any change in kinetic energy is equal to the net work done on an object (W = \text{\Delta} KE).

Law of Conservation of Energy

The law stating that energy cannot be created or destroyed, but can only be transformed from one form to another.

Machine

A device used to multiply forces or alter force directions, which cannot multiply work or energy ($\text{Work Input} = \text{Work Output}$).

Efficiency

The percentage of energy input to a machine that is successfully converted into useful work output ($\text{Efficiency} = \frac{\text{useful energy output}}{\text{total energy input}}$).

Interaction

A mutual action between one thing and another requiring a pair of equal and opposite forces acting simultaneously on each.

Newton's Third Law of Motion

The law stating that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

Action and Reaction Forces

Equal and opposite force pairs belonging to a single interaction that always act simultaneously on two different objects.

Newton's First Law of Motion

The law of inertia stating that an object at rest stays at rest, and an object in motion stays in motion at a constant speed along a straight path, unless acted upon by a net external force.

Newton's Second Law of Motion

The law of acceleration stating that when a net force acts on an object, the object accelerates directly proportional to the net force and inversely proportional to its mass ($a = \frac{F}{m}$).