Definitions Flashcards
Archimedes principle
For an object partially or fully submerged in a fluid the upthrust acting on an object is equal to the weight
Centre of mass
A point where the weight of an object appears to act
Hooke’s law
Force is directly proportional to extension as long as the elastic limit is not exceeded
Density
Mass per unit volume
Electromotive force
Work done per unit charge from when other forms of energy have converted into electrical energy
Principles of superposition of waves
When 2 or more waves meet at a point the resultant displacement at the points is the sum of the displacements of the individual waves
Kirchhoff’s first law
the sum of currents entering a junction is equal to the sum of the current leaving the junction
Kirchhoff’s second law
The sum of e.m.f.s is equal to the sum of the p.d.s in a closed loop
Linear momentum
Mass x velocity
Moment
Force X perpendicular distance from pivot
Newton’s first law
An object will remain at rest or have a constant velocity unless a resultant force acts on it
Newton’s second law
Force is directly proportional to the rate of change of momentum
Newton’s third law
If an object A exerts a force on object B, object B exerts an equal and opposite force on object A of the same type
Photoelectric effect
The emission of photoelectrons from a metal surface when electromagnetic radiation above a threshold frequency is incident on the metal
Potential difference
Work done per unit charge from electrical energy to other forms
Principle of conservation of momentum
Momentum is conserved in a closed system
Principle of moments
When a body is in equilibrium the sum of the moments clockwise is equal to the sum of the moments anti-clockwise
Torque of a couple
One of the forces X perpendicular distance between forces
Young’s modulus
Stress/ strain as long as the elastic limit is not exceeded
Binding energy
Minimum energy required to completely separate a nucleus into protons and neutrons
Boyle’s law
Pressure is inversely proportional to volume for a fixed mass with a constant temperature
Brownian motion
The continuous random motion of small particles suspended in a fluid visible under a microscope
Cosmological principle
The universe is homogenous and isotropic and the laws of physics are universal
Homogenous
Uniform density
Isotropic
In all directions
Coulomb’s law
The electrostatic force experienced by 2 points charges on each other is directly proportional to the product of their charges and inversely proportional to the square if their separation
Electric field strength
The force Experienced per unit positive charge at that point
Electric potential
The work done per unit positive charge to move a charge from infinity to a point in an electric field
Faradays law
The magnitude of the e.m.f induced is directly proportional to the rate of change of magnetic flux linkage
Gravitational field strength
The gravitational force experienced per unit mass at a point within a gravitational field
Gravitational potential
Work done per unit mass to move a mass from infinity to a point in the gravitational field
Hubbles law
Recessional velocity of a galaxy is directly proportional to its distance from earth
Lens’s law
The directional of induced e.m.f or current is always opposite to the change causing it
Magnetic flux density
The strength of a magnetic field
Newton’s law of gravitation
The force between two point masses is directly proportional to the product of the two masses and inversely proportional to the square of the separation
Simple harmonic motion
- Acceleration of an object is directly proportional to its displacement
- Acceleration of an object acts in the direction opposite to displacement
Specific heat capacity
The energy required to increase 1kg of mass by 1 kelvin
Specific latent heat
The energy required to change the phase per unit mass
Wien’s displacement law
Peak wavelength at which the intensity of radiation from a black body is a maximum, is inversely proportion to the absolute temperature of the black body
Internal energy
The sum of randomly distributed kinetic and potential energies of the substance
Kepler first law
The orbit of a planet is an ellipse with the sun at one of the two foci
Keplers second law
A line segment connecting a planet to the sine sweeps out equal areas during equal time intervals
Keplers third law
The square of the orbital period of a planet is directly proportional to the cube of its average distance from the sun
Kinetic model
A model that describes all substances as made of atoms, ions of molecules arranged differently depending on the phase
Inelastic collision
A collision in which kinetic energy is transferred to other forms
Hadron
A particle or antiparticle affected by the strong nuclear force and weak nuclear force e.g. Protons and neutrons
Leptons
Particle and antiparticle not affected by the strong nuclear force but by the weak
Elastic limit
A point where plastic deformation takes place
Plastic deformation
When a material or object will no longer return to its original shape
Electric degeneracy pressure
An outward force provided by electrons in a white dwarf which is caused by the Pauli exclusion principle
Chandrasekhar limit
The maximum mass of a core of a star where electron degeneracy pressure will prevent gravitational collapse of the core 1.44 M
Electron volt
Energy transferred to or from an electron when it passes through a potential difference of one volt
Absolute zero
The lowest possible temperature at which substances have minimal internal energy
One becquerel
An activity of one decay per second
One astronomical unit
The mean distance from the earth to the sun
One light year
The distance travelled by light in a vacuum for 1 year
One parsec
The distance at which 1Au subtends an angle of one arcsecond
Ohms law
Potential difference is directly proportional to current as long as temperature is constant
Magnetic flux density
The force on one metre of wire carrying a current of one amp at right angles to the magnetic field
