IB Physics SL/HL Definitions

The definitions that could be asked for on the IB Physics SL/HL Exam

Displacement

Position of an object relative to its starting position.

Velocity

Rate of change of displacement.

Speed

Rate of change of distance.

Acceleration

Rate of change of velocity.

Newton's First Law

An object continues in uniform motion in a straight line/ at rest unless a resultant force acts.

Newton's Second Law

The acceleration of an object is proportional to and in the same direction as its resultant force.

Newton's Third Law

When 2 objects react, the exert equal and opposite forces on each other.

Linear Momentum

The product of mass and velocity.

Impulse

Change in momentum.

Law of conservation of momentum

Momentum of object in system stays the same in a closed system.

Work

Force X distance moved in direction of force.

Kinetic Energy

The energy an object has due to it's motion

Change in GPE

The energy an object has due to its position above the Earth.

Elastic Collision

KE is conserved and objects bounce off with the same speed it did before in opposite directions.

Inelastic Collision

Maximum loss of KE, objects stick together & momentum is still conserved.

Explosion

Objects move away from each other, internal energy becomes KE.

Efficiency

Ratio of work out: energy put in.

Mole

Amount of substance that has the same number of molecules as the number of of molecules as the number of atoms in 12g of C-12.

Molar Mass

Mass of 1 mole of the substance.

Avogadro's Constant

Number of molecules in 1 mole = 6.022 × 10²³

Specific Heat Capacity

The energy needed to increase the temperature of of 1 kilo of an object by 1K.

Thermal Capacity

The energy needed to increase the temperature of an object by 1K.

Specific Latent Heat

Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.

Pressure

Force per unit area.

Displacement (SHM)

Distance away a particle is from its equilibrium position.

Amplitude (SHM)

Maximum displacement of a particle from its equilibrium position.

Frequency (SHM)

Number of oscillations produced per second.

Period (SHM)

Time taken for a complete oscillation.

Phase Difference (SHM)

The fraction of an oscillation that one wave moves behind another.

Simple Harmonic Motion

Motion where the acceleration of an object is proportional to & in the opposite direction to displacement. a = -ω2x

Damping

Process where the energy of an oscillating system decreases with amplitude by a dissipative force acting in the opposite direction.

Natural frequency

The frequency that a system naturally oscillates at.

Forced oscillation

An oscillation that occurs & stays , Where an object is forced to oscillate by an external force.

Resonance

When the frequency of a driving force matches the natural frequency of oscillation.

Transverse wave

Oscillations are at 90° to direction of energy transfer/ wave motion.

Longitudinal wave

Oscillations are parallel to direction of energy transfer/ wave motion.

Crest

Point on a wave with maximum positive displacement.

Trough

Point on a wave with maximum negative displacement.

Compression

Region (on a wave) where particles are closer together than they would be in their equilibrium state.

Rarefaction

Region (on a wave) where particles are further apart than they would be in their equilibrium state.

Wavelength

The shortest distance between 2 points on a wave that are in phase.

Wave speed

The speed at which wave fronts pass a stationary observer.

Intensity

The power per unit area received by an observer from a wave.

Principle of superposition

When 2 or more waves of the same type meet, the total displacement at a point on a wave is the displacements of the individual waves added at that point.

Constructive/destructive interference

Phase difference is 0/ out of phase& path difference is a whole 'n' of wavelength/ a fraction of it.

Electric potential difference

Work done per unit charge in moving a positive charge from one point in the (electric) field to another.

Electronvolt

The amount of energy an electron gains by moving through a potential difference of 1 volt.

Electric current

The rate of flow of electrical charge.

Resistance

The ratio of voltage across the material to the current flowing through it.

Ohm's Law

The current through a wire is proportional to the p.d. across it; as long as the temperature is constant.

Electromotive force (emf)

The power supplied by the supply per unit current.

Internal resistance

Resistance if a source (of power).

Gravitational field strength

The force per unit mass experienced by a small test mass placed in the field.

Newton's universal law of gravitation

Any point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to their separation².

Electric field strength

The force per unit charge experienced by a small test charge placed in the field.

Magnetic field strength

F=BILsinø Direction: 90° to field lines.

Nuclide

An atom with a particular nucleus configuration.

Nucleon

A proton or a neutron.

Isotope

An element with the same number of protons but a different number of neutrons.

Radioactive half life

The time taken for the total number of nuclei (of a radioactive substance) to halve.

Unified atomic mass

The mass of ½ of the nucleus of a C-12 isotope.

Mass defect

The difference in mass between a nucleus and its separate nucleons.

Binding energy per nucleon

The total binding energy for the nucleus divided by the total number of nucleons

Binding energy

The energy needed to break up a nucleus into its constituent nucleons.

Degraded energy

Energy transferred to surroundings that can no longer do useful work.

Energy density

The mean energy liberated per kg of a fuel.

Fuel enrichment

A process where you increase percentage of U-235 to make fission more likely.

Moderator

Slows down fast neutrons to increase the chance of more reactions. (So they don't pass through the nuclei)

Control rod

This absorbs neutrons to control chain reactions.

Heat exchanger

This allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. The thermal energy is transferred to heat water, and the steam that is produced turns the turbines.

Photovoltaic cell

Light hits semiconductors & electrons are released/ moved; creating an electric field.

Solar heating panel

Heat goes through glass pane & is absorbed by black pipes with running water in them.

Albedo

The ratio of reflected: incident radiation.

Stefan- Boltzmann law

Total power radiated ∝ T⁴ OR P= σAT⁴.

Emissivity

The ratio of power emitted by a body to the power emitted if it was a black body.

Surface heat capacity

The energy needed to raise the temperature of a unit area of a planet's surface by 1K.

Enhanced greenhouse effect

Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities

Coefficient of volume expansion

The fractional change in volume per degree change in temperature.

Gravitational potential

Work done per unit mass in bringing a test mass from infinity to that point in the field.

*Gravitational potential energy

Work done in moving an object from infinity to that point.

Electric potential

The work done per unit charge in bringing a positive test charge from infinity to that point in the field.

Electric potential energy

The work done moving a charge from infinity to a point in an electric field.

Isochoric

Constant volume: no work is done.

Isobaric

Constant pressure: Work done is area under line.

Isothermal

Constant temperature: Work done= area under curve.

Adiabatic

No heat transfer: compression/ expansion. Work is done on/ by gas

Standing waves

Transfer no energy. They have the same amplitude and are in phase. Happens when a wave & its reflection interfere (or just 2 waves)

One dimensional standing wave

Happens when a wave reflects back from a boundary along the route it came.

Doppler Effect

The change in perceived frequency because the source or observer is moving.

Rayleigh criterion

2 points will be resolvable if the first minimum of the diffraction pattern of one source overlaps the central maximum of the diffraction pattern of the second source.

Polarized light

Light with waves that vibrate in 1 plane.

Brewster's angle

Happens when the transmitted ray is 90° to the reflected ray. The angle gives us the angle of incidence needed for plane-polarized light.

Polariser

A device that makes polarized light from an unpolarised beam.

Analyser

A polariser used to detect polarised light.

Optically active substance

A substance that rotates the plane of polarisation of light that goes through it.

Stress analysis

If polarised white light is shone on plastic, you can see the stress points where the coloured lines are.

Magnetic flux

A measure of the strength of a magnetic field over a given area/ number of field lines.

Magnetic flux linkage

The product of the magnetic flux and the number of turns in a given coil.

Faraday's law

The size of an induced emf is proportional to the rate of change of flux linkage.

Lenz's law

The direction of an induced current is such that it'll oppose the change causing it.