OCR A-Level Physics: Motion, Forces, Energy, Materials, and Momentum

Comprehensive vocabulary flashcards covering fundamental mechanics and materials concepts from OCR A Physics, including motion graphs, forces, moments, energy, materials properties, and momentum laws.

Distance

The total length of the path travelled by an object.

Displacement

The change in position of an object in a specified direction.

Speed

A scalar quantity defined as distance travelled per unit time.

Velocity

A vector quantity defined as displacement per unit time, possessing both magnitude and direction.

Average Speed

The total distance travelled divided by the total time taken: $\text{average speed} = \frac{\text{total distance}}{\text{total time}}$.

Average Velocity

The displacement of an object divided by the time taken: $\text{average velocity} = \frac{\text{displacement}}{\text{time}}$.

Instantaneous Speed

The speed of an object measured at one specific moment in time.

Gradient of a Displacement–Time Graph

The velocity of the object.

Gradient of a Velocity–Time Graph

The acceleration of the object.

Area Under a Velocity–Time Graph

The displacement of the object; sections below the time axis represent negative displacement.

SUVAT Equations

A set of kinematic equations used exclusively for straight-line motion with constant acceleration.

Stopping Distance

The total distance travelled before a vehicle stops, consisting of the sum of thinking distance and braking distance.

Mass

A measure of the amount of matter in an object, measured in kilograms ($\text{kg}$).

Weight

The gravitational force exerted on an object, calculated as $W = mg$ and measured in newtons ($\text{N}$).

Centre of Mass

The single point at which an object's mass can be considered to be concentrated.

Free-Body Diagram

A diagram showing all external forces acting on a single isolated object.

Terminal Velocity

The constant falling velocity reached when the drag force equals the weight and the resultant force is zero.

Moment of a Force

The turning effect of a force, given by the force multiplied by the perpendicular distance from the pivot: $M = Fd$.

Principle of Moments

The principle stating that for an object in rotational equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments.

Couple

A pair of equal, opposite, parallel forces acting along different lines that produce a turning effect with zero resultant force.

Triangle of Forces

A closed vector triangle formed by drawing three coplanar force vectors head-to-tail when they maintain an object in equilibrium.

Density

Mass per unit volume of a substance, given by $\rho = \frac{m}{V}$.

Archimedes' Principle

The principle stating that the upthrust acting on an immersed object is equal to the weight of fluid displaced.

Gauge Pressure in a Liquid

The pressure at a depth $h$ due solely to the liquid, given by $p = h\rho g$, where $\rho$ is liquid density and $g$ is gravitational field strength.

Work Done

The energy transferred by a force, calculated as $W = Fs$ for a parallel force, or $W = Fs\cos(\theta)$ when the force acts at an angle $\theta$ to the displacement.

Conservation of Energy

The principle stating that energy cannot be created or destroyed, only transferred between stores.

Kinetic Energy

The energy possessed by an object due to its motion, defined by $E_k = \frac{1}{2}mv^2$.

Gravitational Potential Energy Change

The change in energy of an object when moved vertically near Earth's surface, defined by $\Delta E_p = mg\Delta h$.

Area Under a Force–Displacement Graph

The total work done by the force.

Power

The rate of energy transfer or rate of doing work, defined by $P = \frac{E}{t}$ or $P = \frac{W}{t}$, and as $P = Fv$ for a force acting parallel to velocity.

Efficiency

The ratio of useful output energy or power to total input energy or power: $\text{efficiency} = \frac{\text{useful output}}{\text{total input}}$.

Hooke's Law

The principle stating that extension is directly proportional to applied force up to the limit of proportionality: $F = kx$.

Spring Constant

The force per unit extension of a spring ($k = \frac{F}{x}$), measured in $\text{N}\,\text{m}^{-1}$.

Elastic Potential Energy

The energy stored in a stretched or compressed material, given by $E = \frac{1}{2}Fx = \frac{1}{2}kx^2$ for a Hooke's-law spring, representing the area under a force–extension graph.

Elastic Deformation

A temporary deformation that reverses completely upon removal of the applied load.

Plastic Deformation

A permanent deformation that remains in a material after the applied load is removed.

Limit of Proportionality

The point on a force–extension graph beyond which force is no longer directly proportional to extension.

Elastic Limit

The point beyond which a material will not fully return to its original shape and dimensions when unloaded.

Tensile Stress

The tensile force applied per unit cross-sectional area: $\sigma = \frac{F}{A}$, measured in pascals ($\text{Pa}$) or $\text{N}\,\text{m}^{-2}$.

Tensile Strain

The fractional change in length: $\varepsilon = \frac{\Delta L}{L}$, which is a dimensionless ratio with no units.

Young Modulus

The ratio of tensile stress to tensile strain within the linear region: $E = \frac{\text{tensile stress}}{\text{tensile strain}}$.

Brittle Material

A material that fractures after relatively little or no plastic deformation.

Ductile Material

A material that exhibits a large plastic region and can extend considerably before fracturing.

Newton's First Law of Motion

An object remains at rest or travels at a constant velocity unless acted upon by a resultant force.

Newton's Second Law of Motion

The resultant force equals the rate of change of momentum: $F = \frac{\Delta p}{\Delta t}$ or $F = \frac{dp}{dt}$; for a constant mass, it simplifies to $F = ma$.

Newton's Third Law of Motion

When two bodies interact, they exert equal and opposite forces on different bodies.

Momentum

A vector quantity defined as the product of mass and velocity ($p = mv$), measured in $\text{kg}\,\text{m}\,\text{s}^{-1}$.

Conservation of Momentum

The principle stating that total momentum remains constant in an isolated system with zero resultant external force or impulse.

Impulse

The product of a constant force and the time interval during which it acts ($J = F\Delta t$), equal to the change in momentum ($\Delta p$) and represented by the area under a force–time graph.

Elastic Collision

A collision in an isolated system where both total momentum and total kinetic energy are conserved.

Inelastic Collision

A collision where total momentum is conserved, but some kinetic energy is transferred to other energy forms.