Physics- General Definitions.txt

Position of an object relative to its starting position.

Rate of change of displacement.

Rate of change of distance.

Rate of change of velocity.

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

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

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

The product of mass and velocity.

Change in momentum.

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

Force X distance moved in direction of force.

The energy an object has due to it's motion

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

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

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

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

Ratio of work out: energy put in.

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.

Mass of 1 mole of the substance.

Number of molecules in 1 mole = 6.022 × 10²³

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

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

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

Force per unit area.

Distance away a particle is from its equilibrium position.

Maximum displacement of a particle from its equilibrium position.

Number of oscillations produced per second.

Time taken for a complete oscillation.

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

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

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

The frequency that a system naturally oscillates at.

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

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

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

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

Point on a wave with maximum positive displacement.

Point on a wave with maximum negative displacement.

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

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

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

The speed at which wave fronts pass a stationary observer.

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

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.

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

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

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

The rate of flow of electrical charge.

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

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

The power supplied by the supply per unit current.

Resistance of a source (of power).

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

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.

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

• F=BILsinø
• Direction: 90° to field lines.

An atom with a particular nucleus configuration.

A proton or a neutron.

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

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

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

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

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

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

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

The mean energy liberated per kg of a fuel.

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

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

This absorbs neutrons to control chain reactions.

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.

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

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

The ratio of reflected: incident radiation.

Total power radiated ∝ T⁴ OR P= σAT⁴.

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

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

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

The fractional change in volume per degree change in temperature.

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

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

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

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

Constant volume: no work is done.

Constant pressure: Work done is area under line.

Constant temperature: Work done= area under curve.

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

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

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

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

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.

Light with waves that vibrate in 1 plane.

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

A device that makes polarized light from an unpolarised beam.

A polariser used to detect polarised light.

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

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

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

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

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

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

All particles have a wave like nature.

An electron has possible wavelengths like a standing wave on a string so electrons have discrete energies.

This gives the probability of where the electron could be (probability regions called orbitals).

• You can only know 1 from each pair:
• -momentum & position
• -energy & time

Probability of decay of a nucleus per unit time

The activity of a radioactive sample ∝ Number of radioactive nuclei present.

Charge per unit p.d. that can be stored on a capacitor.

The ratio of the number of photoelectrons emitted: the number of photons incident on the pixel.

The ratio of the length of the image on the CCD: the length of the object.

A group of stars that are physically near each other in space.

A pattern of stars as seen from Earth that aren't physically near each other in space.

The distance that light travels in 1 year.

The total power emitted by a star.

The power received per unit area on Earth by a star.

A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.

• -Red
• -Comparatively cool
• -Large
• -Fuse elements other than Hydrogen

• -Red
• -Large Mass
• -Large Surface Area
• -Large Luminosity
• -Low Surface Temperature

• -Very Small/ Low Surface Area
• -Large Surface Temperature
• -White

Stars can be distinguished using a telescope

Analysis if its light spectrum shows 2 different classes of stars- the wavelengths show a periodic splitting in frequency.

Analysis of the brightness of its light spectrum shows periodic dips. This is because on star is in the way of the other.

A unit of distance that is equal to 3.26 light years

How bright a star appears from Earth.

The apparent magnitude a star would have if it was 10 parsecs away.

The theoretical density of the universe that would create a flat universe.

The recessional velocity of a galaxy ∝ its distance away from Earth.

2Hz - 20KHz

Amount of energy that a sound wave brings to a unit area every second.

• 10 lg (I / I0);
• where I0 = 1.0 × 10-12 Wm-2.

The probability of a single photon being absorbed in 1 m of the material- use defining equation.

The half-value thickness is that thickness of material which will reduce the intensity of the (transmitted) beam by 50%

The product of of the density of a substance and the speed of sound in that substance.

The total ionized charge produced in unit mass of air by a particular radiation. Q=mX.

The energy absorbed per unit mass of tissue. E=mD.

This allows doses of different types of radiation to be compared for their biological effects.

The amount of energy absorbed

• The time it takes for the activity of a sample
• to halve.

The time it takes the body to naturally eject half of an ingested sample of a radioactive isotope.