IB SL Physics Definitions + Things to remember!

A collection of bodies that are gravitationally bound to the sun (planets

A collection of billions of stars

A collection of galaxies held together by gravity

A collection of stars held together by gravity

A collection of stars which are not necessarily close together, and form a recognisable group

A star not gravitationally bound by another

The mean earth-sun distance

The distance light travels in a year

The apparent movement of a nearby object against the background as seen from two positions

The difference in angular positions

The total power output of a star (amount of energy radiated by a star per second)

The power output per unit area at a given distance

A perfect absorber and emitter of radiation

The wavelength at peak intensity for a black body is inversely proportional to the surface temperature

A star that varies in brightness over a period of days

Mass < 1.4M

Mass > 2.5M

There is a linear relationship between the recessional velocity of a galaxy and its distance

The density that will stop the expansion of the universe (value where universe will contract)

The relative expansion rate of the universe

The energy needed to completely separate a nucleus into its nucleons

• Most of the mass of an atom is confined within a very small volume/nucleus

• All the positive charge is confined within a very small volume/nucleus

• Electrons orbit the nucleus in circular orbits

An error that is identical for each reading

Measurements are above and below the true value with equal probability

A graph of 2 directly proportional quantities will be a straight line through the oirign

Produces a straight line graph

Y is proportional to 1/x or yx=constant

A high number of significant figures with a small spread of results

Near true value

Quantity with magnitude and direction

Quantity with magnitude only

The distance moved in a stated direction (distance and direction from starting point)

Rate of change of distance (per unit time)

Rate of change of displacement

Rate of change of velocity

Change in distance/displacement divided by one particular instant of time

Change in distance/displacement divided by time taken over a period of time

Shape of the path that a moving object makes in the air

An object continues in uniform motion or a straight line, or at rest, unless a resultant external force acts on it

Force = mass x acceleration

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

No resultant force in any direction (translational); No resultant momentum at any point (rotational)

Mass x velocity

Force x time or change in momentum

In an isolated system, momentum is constant

Force x distance moved in direction of force

The energy a body possesses by virtue of its motion

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

When there is a change in kinetic energy

When there is no change in kinetic energy

Rate at which energy is transferred (or rate at which work is done)

Ratio of useful energy to energy transferred

A property that determines the direction of heat flow from two bodies in thermal contact. It measures average random kinetic energy of particles of a substance

Celsius + 273

Proportional to average kinetic energy of particles

Energy that is transferred by a temperature difference

Total potential energy + random kinetic energy in a substance

Amount of energy needed to raise temperature of object by 1 kelvin

Amount of thermal energy needed to raise temperature of unit mass of a substance by 1 kelvin

Amount of thermal energy needed to change the state of unit mass of a substance at constant temperature

Amount of substance that contains same number of units that are in 12g of carbon-12 (6.022*10^23)

Mass of one mole of a substance

Number of atoms in 0.012 kg of Carbon 12 (6*10^23)

Normal force to an area per unit area

Gas consists of a large number of molecules; molecules move with a range of speeds; the volume of the molecules is negligible compared with the volume of gas itself; the collisions of the molecules with each other and the container are elastic; molecules exert no forces on each other or the container except when in contact; the duration of collisions is very small compared with the time between collisions; the molecules obey Newton's laws

Show direction of energy transfer of a wave

Highlight the part of a wave that is moving together (in phase)

Distance any point on a wave has moved from it's undisturbed position

Maximum displacement from mean position

Time taken for one complete oscillation

Number of oscillations that take place per unit time

Shortest distance along a wave between the points that are in phase

Time difference by which one wave leads or lags another

Speed at which wave fronts pass a stationary observer

Average amount of energy transported by a wave in the direction of wave propagation, per unit area per unit time

When 2 or more waves meet, the resultant displacement is the sum of individual displacements

Periodic motion in which the restoring force/acceleration is proportional to the displacement and in the opposite direction

Oscillations parallel to direction of energy transfer

Oscillations are perpendicular to direction of energy transfer

Light in which electric field vector vibrates in one place only

Between 2 points, is work done per unit charge to move a small positive charge between two points

Rate of flow of electrical charge

Total energy difference per unit charge around the circuit (PD When no current flows in a circuit)

Energy gained by an electron when moving through potential difference of one volt

Ratio between potential difference across component/circuit and current through it

When temperature is constant, the current through metallic conductor is proportional to potential difference across it

1 joule per coulomb

Force per unit charge on a small positive test charge

Average speed attained by a particle due to an electric field

1. Current flowing towards a junction = total current flowing away from junction

2. Sum of EMF in any closed loop = sum of potential drops in the loop

Gravitational force between 2 point masses is proportional to the product of 2 masses and inversely proportional to their distance squared

Force exerted per unit mass on small point mass at a location

Source of energy in usable form

Power per unit area emitted by a body is proportional to the absolute temperature ^4

Energy obtained from unit volume

Energy obtained from unit mass

Ratio of energy emitted (per unit area) of a body to energy emitted by a black body of same dimensions at same temperature

Energy required to increase temperature of 1 m^2 of surface by 1 kelvin

Minimum mass needed to sustain fission

Particle in the nucleus of an atom (proton or neutron)