A2 definitions Flashcards
Gravitational potential at a point
- Work done per unit mass
- Work done in moving unit of mass from infinity to that
point
Gravitational force
Force acting between 2 masses in a gravitational field
Newton’s Law of Gravitation
Gravitational force ∝ product of two point masses and 1/∝ the square of separation btw 2 point masses
Gravitational field strength
Force per unit mass
Line of gravitational force
Direction of force on a small test mass
Field of force / Gravitational field
Region of space where a particle experiences a force
Radian
Angle subtended at the centre of circle where arc length is equal to radius
Angular frequency (w)
Angular frequency = 2π x frequency
Oscillations
backward and forward motion btw 2 limits
Damping
Loss of energy
Natural frequency of vibration of a system
Frequency at which body will vibrate when there is no resultant external resistive force acting on it
Free oscillations
Body oscillates without external force acting on it
Forced oscillations
Body is made to vibrate by an external periodic force
Displacement of the mass on the spring
Distance from a ref point in a given direction
Forced frequency
Frequency at which the object is made to vibrate
Weightless
- Gravitational F provides centripetal F.
- Gravitational F is equal to centripetal F.
- Weight is the difference btw gravitational F and
centripetal F, which is zero
Resonance
Max amplitude of vibration of oscillating body when forced freq equals to natural freq of vibration
Simple harmonic motion
- Acceleration ∝ displacement from a fixed point
- provided that acceleration and displacement are in opp
directions
Specific Latent heat
Thermal E per unit mass to change state at constant temp
Specific Latent heat of fusion
Thermal E per unit mass to cause change of state btw solid and liquid at constant temperature
Specific heat capacity
Thermal E per unit mass to raise the temp of a substance by 1°
Thermal equilibrium
Bodies are at the same temperature
For a system, what is meant by :
- +q
- +w
- heat E transferred TO the system
2. external work done ON the system
△U = q + w
- △U
- +q
- +w
- △U = ↑ in internal energy
- +q = heat E transferred TO the system
- +w = work done ON the system
T
absolute temperature
Avogadro constant, NA
Number of atoms in 12g of carbon-12
mole
Amount of substance containing 6.02x1 0^23 particles
Mean-square-speed of atoms
Ideal gas
- Gas obeys the formula PV/T = constant, at all values of p,
V, T. - where p is pressure, V is volume of gas, T is temperature
in K
Internal Energy of system
Total Ep and Ek of molecules in random distribution
Electric Field Strength
Force per unit +ve charge
Electric potential at a point
Work done per unit charge. Work done is moving positive charge from infinity to that point
Coulomb’s Law
Force ∝ product of point CHARGES and 1/∝ to the square of separation btw two point CHARGES
Electric field
Region where a charge experiences an electric force
Capacitance of parallel plate capacitor
- Charge per unit potential.
- Charge; the amount of charge on 1 plate
- Potential; potential difference btw 2 plates
Quantisation of charge
Charge exists in discrete and equal quantitites
n
number of charge carriers per unit volume
Capacitance
charge per unit pd
Magnetic flux density
Force per unit current per unit length of wire, where current is normal to magnetic field
Magnetic flux linkage
(Magnetic flux density) x (cross-sectional A normal to magnetic flux density) x (number of turns on coil) x sin(angle btw B and A)
Magnetic flux
Product of flux density and area where direction of flux is normal to area
Tesla
Newton per ampere per metre when magnetic field is normal to current
Magnetic field
Region where a current-carrying conductor experiences a force
Faraday’s law of electromagnetic induction
Induced emf ∝ rate of △ of magnetic flux linkage
Lenz’s law
Induced emf acts in such a direction to oppose the △ causing it
Smoothing
Output p.d does not fall to zero
Ideal transformer
No power loss in transformer
Work Function Energy
Min photon E required to remove an e- from a surface with 0 Ek
Photon
Quantum of E of electromagnetic radiation
Photoelectric effect
Emission of e- when electromagnetic radiation incident on its surface
de Broglie wavelength
Particles with a wavelength associated with it, which the wavelength is dependent on its momentum
Threshold frequency
Min freq of electromagnetic radiation for the emission of e- from a surface
Mass defect of a nucleus
Difference btw mass of nucleus and mass of constituent nucleus where nucleons are separated to infinity
Random
Time at which a nucleus decays cannot be predicted
Spontaneous
Decay of a nucleus is not affected by environmental factors
Binding energy per nucleus
Min E required to separate the nucleons to infinity
Nuclear binding energy
Min E required to separate nucleons in a nucleus to infinity
Random decay
Decay is unpredictable
Decay constant
Probability of decay of a nucleus per uni time
Nuclear fission
- A single large nucleus divides to form small nuclei.
- Fission is initiated by neutron bombardment
Nuclear fusion
- Two nuclei combine to form a single nucleus
- Fusion is initiated by very high temperatures
Radioactive decay
Unstable nucleus emits particles spontaneously and particles are ionising
Radioactive
Unstable nucleus emits ionising radiation sponstaneously
Isotopes
Atoms of the same element w the same no. of protons ut different no. of neutrons
Gamma radiation
Photons of electromagnetic radiation emitted from nuclei
Nucleus
Small central part of an atome
Nucleon
Proton and neutron contained within a nucleus
Attenuation
Loss of intensity of the wave
Geostationary orbit
Equatorial orbit above the equator where satellite moves from west to east and has period of 24 hours
Geostationary satellite
Satellite is in equatorial orbit traveling from west to east with period of 24 hours
Specific acoustic impedance
Product of density of medium and speed of ultrasound in medium
Hardness of X-ray beam
Penetration of beam.
Greater hardness means great penetration
α
Ratio of reflected intensity / incident intensity
Z2 and Z1
Specific acoustic impedances of media on each side of the boundary
Sharpness
Clarity of resolution of images
Contrast
Difference in degree of blackening btw structures
Linear absorption coefficient
- Parallel beam in matter.
- I = I0 exp(-µx)
- Where I is intensity transmitted, I0 is initial intensity, µ is
attenuation coefficient of the material, and x is thickness
of material
Radioactive half life
- Time for the no. of atoms / activity to be reduced to one half of the original value
radiant flux density
radiant power passing normally thru a SA per unit area
