Eduquas Alevel physics definitions - Option - physics of sport

Scalar

A quantity that has magnitude only.

Vector

a quantity that has magnitude and direction.

Density of a material

Mass divided by volume, mass per unit volume (p)

The principle of moments

The force multiplied by the perpendicular distance from the point to the line of action of the force, i.e. moment = F x d.

Centre of gravity

The single point within a body at which the entire weight of the body may be considered to act.

Displacement

The shortest distance from point A to point B, together with the direction.

Mean speed

Total distance travelled divided by total time taken. Unit: m s-1.

Instantaneous speed

The speed of an object at a specific moment in time. Unit: m s-¹.

Mean velocity

The average rate of change of displacement. Unit: m s-¹.

Instantaneous velocity

The velocity of a body at a specific moment in time. Unit: m s-¹.

Mean acceleration

Change in velocity divided by time taken. Unit: m s-².

Instantaneous acceleration

The rate of change of velocity at a specific moment in time. Unit: m s-².

Terminal velocity

The constant, maximum velocity of an object when the resistive forces on it are equal and opposite to the accelerating force.

Force, F

A push or a pull acting on the body from some external body. Unit: N.

Newton's 3rd law

If a body A exerts a force on a body B, then B exerts an equal and opposite force on A.

Momentum

An object’s mass multiplied by its velocity. (p = mv). Unit: kg m s-¹ or Ns.

Newton's 2nd law

The rate of change of momentum of an object is proportional to the resultant force acting on it.

The principle of conservation of momentum

The vector sum of the momenta of bodies in a system stays constant even if forces act between the bodies, provided there is no external resultant force.

Elastic collision

A collision in which there is no change in total kinetic energy.

Inelastic collision

A collision in which kinetic energy is lost.

Work done

The product of the magnitude of the force and the distance moved in the direction of the force. Unit: J.

Principle of conservation of energy

Energy cannot be created or destroyed, only transferred from one form to another.

Potential energy, Ep

Energy possessed by an object by virtue of its position. Unit: J.

Kinetic energy, Ek

Energy possessed by an object by virtue of its motion. Unit: J.

Elastic potential energy

Energy possessed by an object when it has been temporarily deformed due to forces acting on it. UNIT J

Power, P

The work done per second, or energy transferred per second. Unit: W [= J s-¹].

Period, T

Time taken for one complete cycle

Radian

A unit of measurement of angles equal to about 57.3°, equivalent to the angle subtended at the centre of a circle by an arc equal in length to the radius.

Simple harmonic motion (shm)

A type of periodic motion where the restoring force is directly proportional to the displacement.

Angular velocity (w)

For an object describing a circle at uniform speed, equal to the angle swept out divided by time, rate of change of angle with respect to time

Simple Harmonic Motion (SHM)

occurs when an object moves such that its acceleration is always directed toward a fixed point and is proportional to its distance from the fixed point. (a = - w²x)

Amplitude (A)

The maximum value of the object's displacement (from its equilibrium position).

Frequency (f)

The number of oscillations per second. UNIT: Hz

Free oscillations

occur when an oscillatory system (such as a mass on a spring, or a pendulum) is displaced and released.

Damping

the dying away, due to resistive forces, of the amplitude of free oscillations.

Critical damping

the case when the resistive forces on the system are just large enough to prevent oscillations occurring at all when the system is displaced and released. In SHM

Forced oscillations

These occur when a sinusoidally varying 'driving' force is applied to an oscillatory system, causing it to oscillate with the frequency of the applied force.

Resonance

If, in forced vibrations, the frequency of the applied force is equal to the natural frequency of the system, the amplitude of the resulting oscillations is large.

Ideal gas

A gas which strictly obeys the equation of state PV = nRT, where n is the number of moles, T is the kelvin temperature, and R is the molar gas constant.

The mole

the S.I. unit of an 'amount of substance'. It is the amount containing as many particles as there are atoms in 12 g of carbon-12.

Avogadro constant

6.02 x 10²3 mol-¹

Internal energy (U)

This is the sum of the kinetic and potential energies of the particles of a system.

Heat (Q)

This is energy flow from a region at higher temperature to a region at lower temperature, due to the temperature difference.

First law of thermodynamics

U = Q - W in which Q is the heat entering the system and W is the work done by the system.

Specific heat capacity (c)

The heat required, per kilogram, per degree Celsius or Kelvin, to raise the temperature of a substance. UNIT: J kg-¹ K-¹ or J kg-¹ °C-¹.

Electric current

This is the rate of flow of electric charge. I = ΔQ/Δt. Unit: A.

Efficiency of a system

= 100 × (useful work out / work put in). Unit: none.

Potential difference (pd) (V)

The energy converted from electrical potential energy to some other form per coulomb of charge flowing from one point to the other. Unit: V [= J C-¹].

Ohm's law

The current in a metal wire at constant temperature is proportional to the pd across it.

Electrical resistance (R)

The opposition to the flow of electric current.

Resistivity (ρ)

A measure of how strongly a material opposes the flow of electric current.

Superconducting transition temperature (Tc)

The temperature below which a material exhibits superconductivity.

The law of conservation of electric charge

The total electric charge in an isolated system remains constant. Charge cannot be created or destroyed, though positive and negative charges can neutralize each other.

Electromotive force (Emf) (E)

The energy provided by a cell or battery per coulomb of charge.

Capacitor

A device used to store electric charge.

Capacitance (C)

The ability of a capacitor to store charge per unit voltage.

Dielectric

A material that increases the capacitance of a capacitor when placed between its plates.

Hooke's law

The force exerted by a spring is directly proportional to the distance it is stretched or compressed.

Spring constant

A measure of the stiffness of a spring. Force per unit extension

Resistance

Potential difference across a region divided by the current through it

Unit of Resistance

VA-¹

Resistance of a metal wire

Given by pL/A, where p is the resistivity, a constant for the material at constant temperature.

Unit of Resistivity

Ω m

Superconducting

When a material loses all its electrical resistance due to being at a very low temperature

Electromotive force (emf)

The energy converted from another form to electrical potential energy per coulomb of charge flowing through the source.

Unit of emf

V

A capacitor

A pair of conducting plates separated by an insulator that acquires equal and opposite charges when a potential difference is applied.

Unit of Capacitance

F [= C V-1]

Insulator in a capacitor

The role of the dielectric material between the plates that increases capacitance compared to empty space.

Spring tension

It is proportional to a spring’s extension from its natural length.

Unit of Spring constant

N m-¹

Stress

The force per unit cross-sectional area when opposing forces act on a body.

Unit of Stress

Pa or N m-²

Strain

The extension per unit length due to an applied stress.

Young's modulus

E = tensile stress / tensile strain, defined for the Hooke's law region.

Unit of Young's modulus

Pa or N m-²

Crystalline solid

Solid in which atoms are arranged in a regular array with long-range order.

Amorphous solid

Solid with atoms arranged randomly, lacking long-range order.

Polymeric solid

A solid made up of chain-like molecules.

Ductile material

Material that can be drawn out into a wire, implying plastic strain occurs under stress.

Elastic strain

Strain that disappears when the stress is removed.

Plastic (or inelastic) strain

Strain that decreases only slightly when the stress is removed.

Elastic limit

The point at which deformation ceases to be elastic.

Dislocations

Certain faults in crystals that reduce the stress needed for planes of atoms to slide.

Grain boundaries

The boundaries between crystals in a polycrystalline material.

Ductile fracture

The fracture process preceded by local thinning.

Brittle material

Material with no region of plastic flow, failing by sudden fracture under tension.

Brittle fracture

Fracture under tension by means of crack propagation.

Elastic hysteresis

When a material like rubber is stressed and the stress is relaxed, the stress-strain graphs form a loop.

Newton's law of gravitation

The gravitational force between two particles is proportional to the product of their masses and inversely proportional to their separation squared.

Gravitational constant

G = 6.67 x 10-11 N m² kg-².

Coulomb's law

The electrostatic force, F, between two small bodies is proportional to the product of their charges, Q₁ and Q₂, and inversely proportional to their separation squared, F = k * (Q₁ * Q₂) / r².

Electric field strength, E

The force experienced per unit charge by a small positive charge placed in the field. Unit: V m⁻¹ or N C⁻¹.

Gravitational field strength, g

The force experienced per unit mass by a mass placed in the field. Unit: m s⁻² or N kg⁻¹.

Electric potential, Vₑ

The work done per unit charge in bringing a positive charge from infinity to that point. Unit: V or J C⁻¹.

Gravitational potential, Vg

The work done per unit mass in bringing a mass from infinity to that point. Unit: J kg⁻¹.

Black body

A body (or surface) which absorbs all the electromagnetic radiation that falls upon it.

Absolute Zero

At -273.15°C the energy of particles in a body is the lowest it can possibly be.

Stefan's law

The total electromagnetic radiation energy emitted per unit time by a black body is given by power = AσT⁴.

Luminosity of a star

The total energy a star emits per unit time in the form of electromagnetic radiation. Unit: W.