Definitions Flashcards
Distance (m)
How far you have travelled
Displacement
Distance travelled in a particular direction
Speed
Rate of change of distance
Velocity
Rate of change of position
Acceleration
Rate of change of velocity
Projectile
An object moving through the air under the influence of only gravity
Resultant force
Sum of all forces acting on an object
Surface friction
The force that opposes motion between the surfaces of two solid objects
Viscous drag
Drag force acting on a moving object due to the viscocity of the fluid it is moving through
Bouyancy
The ability of a fluid to provide a vertical upwards force on an object placed in or on it
Gravitational Field
A region of space where an object will experience a force due to its mass
Linear momentum
Product of mass and velocity of an object
Elastic collision
No kinetic energy is lost
Centripetal force
Unbalanced force that acts to create circular motion
Mechanical energy
Energy possessed by an object due to its motion or position
Work
Transfer of energy
Efficiency
Ratio of how much useful energy/work or power we get out of a system
Isochronus
Oscillation repeats with the same time period
Amplitude
Maximum displacement from equilibrium position
Frequency
Number of oscillations per second
Period
Time for one complete oscillation
Phase
Measure of how in step different particles are
Simple harmonic motion
Type of oscillation that takes place when the acceleration of and the force on an object are proportional to the displacement and in the opposite direction
Longitudinal waves
Vibrate parallel to the direction of energy transfer
Transverse waves
Particles vibrate at right angles to direction of energy transfer
Mechanical waves
Need a medium to travel through
Electromagnetic waves
Do not need a medium to travel through, are all transverse waves, can travel through a vacuum, 3x10^8 ms-1
Angular velocity (w)
Angular displacement divided by time taken
Energy
Capacity to do work
Gravitational potential energy
Is due to the position of an object when close to the surface of the Earth
Elastic potential energy
Energy stored in an object that has been deformed elastically
Temperature
Measure of the average random Ek of the molecules in an object
Internal energy
Total intermolecular potential energy and total random Ek of the molecules
Specific heat capacity
The amount of energy required to raise the temperature of the unit mass of a substance by 1K
Specific latent heat
Amount of energy per unit mass of a substance absorbed or released during a change of phase without a change in temperature
Thermal conduction
Transfer of energy without any overall movement of molecules or atoms
Thermal conductivity (K)
Measure of how good a thermal conductor is at transferring energy through itself
Convection
Thermal energy is transferred by the bulk movement of molecules/atoms
Thermal radiation
Emission of electromagnetic radiation by an object
Emissivity (e)
How close to a black body an object is
Albedo
The proportion of incident radiation reflected
Solar constant
The amount of solar energy that falls per second on an area of 1m^2 above the Earth’s atmosphere
Current
Rate of flow of electric charge
Electric potential difference
The work done or energy transferred per unit charge on moving a positive charge between two points along the path of the current
Resistance
Ratio of the potential difference across a component to the current flowing through it
Ohm’s Law
The current flowing through a piece of metal is proportional to the potential difference cross it providing the temperature remains constant
Electrical power
The amount of energy used or supplied per unit time
EMF
Energy supplied per unit charge by the cell to the circuit
Phase
A measure of how in step different particles are
Simple harmonic motion
A type of oscillation tat takes places when the acceleration of and force on an object is proportional to the displacement and acts in an opposite direction
Angular frequency
This is the angular speed that an object undergoing circular motion would have if it were to match SHM (rads-1)
Longitudinal wave
Particles vibrates parallel to the direction of energy transfer
Transverse waves
Particles of the medium vibrate at right angles to the direction of energy transfer
Displacement position graphs
Shows the displacement of a range of particles along the length of the medium
Displacement time graphs
Motion of one particle of the medium over a period of time
Mechanical wave
Needs a medium to travel through
Electromagnetic waves
Do not require a medium to travel through, all transverse waves, travel at 3x10^8
through a vacuum
Total internal reflectionn
When light is travelling from a more to less optically dense medium and angle of incidence is greater than the critical angle
Diffraction
When waves move past an obstacle or through a gap and spread out
Constructive interference
When two waves meet in phase and form a resultant wave with amplitude equal to sum of the two waves
Destructive interference
When two waves meet 180* out of phase and cancel out to give a wave of 0 amplitude
Principle of superposition
If two or more waves meet, the resultant displacement at any point is found by adding the displacements produced by each individual wave
Standing waves
When two waves of the same type meet and have the same amplitude, the same frequency and travelling in opposite directions
Resonant frequency
Natural frequency at which they oscillate
Resonance
If a system is forced to oscillate at it’s natural frequency, there is a large increase in the amplitude of the osciallations
Damping
Dissipation of energy from an oscillator due to resistive forces
Doppler effect
Change in observed frequency of a wave when there is relative motion between the wave source and the observer
Newton’s Universal Law of Gravitation
Every single point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of their seperation
Gravitational field
A region of space where a mass experiences a force because of it’s mass
Gravitational field strength
The force per unit mass experienced by a small point mass placed at that point
Kepler’s First Law
Planets move on ellipses with the Sun at one foot of the ellipse
Kepler’s Second Law
The line joining a planet and the Sun sweeps equal areas in equal times
Kepler’s Third Law
The square of the orbital period of a planet is directly proportional to the cube of the semimajor axis of its orbit (PROOF Fc=Fg, mw^2=(GMm/r^2), m^4pi^2r/T^2 = GMm/r^2, r^3=(GM/4pi^2) T^2. G, M, 4, pi are all constant, r^3 prop to T^2)
Conservation of Charge
Charge cannot be created or destroyed
Coulomb’s Law states that…
Force between two point charges is proportional to the product of their charges (q1 and q2) and inversely proportional to the square of their separation (r)
Electric field
A region of space where a charged object experiences a force due to its charge.
Electric field strength
Force per unit charge experienced by a small positive charge placed in the field.
Solenoid
When a wire is coiled up and each turn of the wire interacts to create a stronger field
Strong nuclear force
Force that acts at a short range between nucleons. Balanced by electrostatic repulsion between protons
Isotopes
Different nuclei of an element that have a different number of neutrons but the same number of protons
Atomic Energy levels
Discrete energy levels around a nucleus that electrons exist in
Photons
A particle that is a packet of energy
Alpha particle
A helium nucelus
Beta particle
Positive - positive electron/positron
Negative - an electron emitted from the nucleus
Gamma radiation
Electromagnetic radiation
Half life
Time take for half of the nuclei in a sample to decay (or the activity to fall to 50% of the initial value)
Nuclear equations
Show how nuclei change during radioactive decay
Background radiation
Radiation from a number of sources that must be subtracted from any measurements of radiation of an experimental sample
Nuclear fission
When larger nuclei break into smaller nuclei (can happen spontaneously or when nuclei is bombarded with neutrons)
Nuclear fusion
When temp and pressure is high enough, small nuclei overcome electrostatic repulsion and form larger nuclei
Unified atomic mass unit
Equivalent to the 1/12 of the mass of a carbon-12 atom
Mass defect
The difference in mass between the total mass of all of the individual nucleons and their total mass when bound in the nucleus
Binding energy
The amount of energy required to break apart a nucleus into seperate nucleons
Chain reaction
When neutrons from fission collide with further uranium nuclei to sustain fission
Chandrasekhar limit
Electron degeneracy pressure (electrons cannot be packed in any closer due to gravity) so max mass of white dwarf stars is 1.4M.
Oppenheimer-Volkoff limit
Neutron degeneracy pressure (neutrons cannot be packed in any closer due to gravity) so max mass of neutron stars is 3M.
Instability strip
Region of stars that vary in size and luminosity due to periodic expansion and contraction
Parallax angle
Half of the observed angular displacement of a star
Parsec
The distance at which the angle subtended by the radius of the Earth’s orbit is one arc second
