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Things I have learnt from doing past papers

a m Physics A level English 123 cards

Cards in this deck (123)

  1. 1Gravitational force between two spheres in contact?Still an attractive force between them, the separation (r) is the sum of their radii.
  2. 2Total momentum of explosion?Sum of the momentum of components (Mu+Mu) assuming no external forces are applied.
  3. 3Momentum after an elastic collision?Momentum after collision - (-momentum before collision) = 2mv
  4. 4Energy changes during a complete oscillation of a bob on a simple pendulum?Max Gravitational Potential - transferred to kinetic- Max Kinetic - transferred to gravitational - Max Gravitational Potential (max displacement again)
  5. 5Displacement vs Amplitude of a bob on a pendulumDisplacement = vertical distance from original position , Amplitude = horizontal distance from original position
  6. 6Simple Pendulum Ek Graph against timeEk peaks at 1/4 T and 3/4 T (assuming initial max displacement) sine wave.
  7. 7Voltage after one time constantInitial Voltage/e
  8. 8Higher initial pd affect on capacitors ability to store energyIf V is doubled, E stored will be 4 times greater.
    E= 1/2 C x V squared
  9. 9Higher initial pd affect on capacitors energy loss time.No affect, discharge time depends only on time constant, R and C, not v.
  10. 10Path of mass on string whirled round at increasing speed until string breaksparabola in the vertical plane
  11. 11Ek of Particle moving in circle of radius r at uniform speed with the time period t2 pie squared x m x r squared / T squared
  12. 12Electron at constant speed entering at right angles to uniform magnetic fieldCircular arc in plane perpendicular to the direction of the magnetic field.
  13. 13Current directionThe way a positively charged particle would move, from the positive to negative terminal
  14. 14coil rotation speed doubledflux changes twice as fast, emf induced is twice as much, twice the number of oscillations
  15. 15electron travelling in same plane as magnetic field is actingfor a force to act on a charge, the electron and the magnetic field lines must not be in the same plane, otherwise they remain unaffected and no force is applied
  16. 16centripetal force and the force between two masses (planet and satellite)GMm/r2 = mw2r , therefore because the gravitational force is equal to the centripetal force r3= Gm/w2
  17. 17Quark composition of a mesonquark antiquark pair
  18. 18Strangeness in the weak interactionnot conserved
  19. 19Decay of a k mesonproduces an electron or muon, produces a pie meson, produces an neutrino or antineutrino through w boson (depending on charge)
  20. 20Roles exchange particles play in an interactionthey exchange momentum and energy, transfer charge sometimes
  21. 21Ranges of exchange particlesy boson has infinite range, w boson has very short range, pie meson has range of 3- 4fm
  22. 22strange particlescontain strange quarks
  23. 23hadrons and leptonsboth affected by the weak, hadrons affected by strong also
  24. 24an alpha particleis a helium nucleus
  25. 25when you remove electrons and add electrons what happenspostive ion (remove) or negative ion (add) is formed
  26. 26how many protons and neutrons will a stable atom havethey will have the same number of protons and electrons if stable. Less protons than electrons if negative, and if positive, less electrons than protons
  27. 27specific chargeratio of charge to mass of nucleus
  28. 28why does a w+ boson decay into a neutrino rather than an antineutrinoconservation of lepton number
  29. 29A positrons mass or beta particleis the same as an electrons rest mass
  30. 30Why do kinetic energies of emitted electrons vary up to a maximum valuethe energy required to remove the electron can vary depending on how deep it is, but the ek will never be bigger than the energy from the photon - the work function.
  31. 31unit of work functionj or ev
  32. 32Minimum time taken for electron to absorb an amount of energyenergy required to liberate electron/ total energy supplied
  33. 33validated evidenceresults of an experiment proven and replicated by other scientists, and an experiment observation needs to be observed
  34. 34why can threshold frequency not be explained by wave theorybecause the energy of a wave increases with its intensity, wave theory can also not explain why there is no time delay on photoelectric emission
  35. 35How do we calculate how many different wavelengths of radiation are emitted when an atom returns to the ground statemark all the possible configurations of photon transfer from energy level to level
  36. 36how does energy release affect wavelength as an atom returns to the ground statethe smallest energy releases as a photon is released will create the longest wavelengths because wavelength= hc/e
  37. 37mercury at low pressureconducting
  38. 38excitation by photon absorptionphotons need to have exactly the energy that is the difference between energy levels, they need to have a certain frequency for this and electrons must absorb all of this photon energy
  39. 39experiments that show wave like nature of electronsdiffraction experiements
  40. 40why is it easier to demonstrate the wave properties of electrons than protonselectrons are easier to obtain and accerlerate
  41. 41ev to joules1ev = 1.6 x 10 -19 joules
  42. 42unit of momentumNs or Kgms-1
  43. 43what happens in a superconductoras it cools resistivity decreases to zero (critical temp)
  44. 44what would we measure the diameter of a wire withvernier calliper or micrometer
  45. 45when calculate the current through a component what do we consideronly the resistance of the component (or something its in series with), the pd through it is the circuit pd - any components in series with it
  46. 46filament bulb graphobeys ohms law at low voltages, straight gradient through origin. a decreasing gradient curve is seen in the negative quadrant, the rate of change of i to v decreases with gradient.
  47. 47voltage in series and parallelvoltage across series is shared. Voltage across parallel is the same.
  48. 48if you decrease the length of a wire and increase its area what happens to its resistancelength decrease = resistance decrease area increase = resistance decrease
  49. 49testing a diodeprotective resistor before diode, connect up circuit, voltmeter across diode, obtain range of results, 0.6 voltage, reverse connections for reverse bias, ranges may need to be changed bc current so small
  50. 50low internal resistance in a rechargeable batteryless energy wasted, quicker recharge
  51. 51to find total currentI = v/r , take the emf and add all the resistances including internal x circuit current
  52. 52straight line equation for vv= Ir - e
  53. 53low internal resistance in carsneeds a large current to start, low internal resistance minimises pd loss and keeps current big
  54. 54net emf's in parallelvoltage in parallel is the same, so is emf
  55. 55current in parallelshared
  56. 56what provides more electrical energy emf in parallel or seriesemf in series have greater charge due to same current, parallel has smaller charge due to shared current. w = V X Q ,
  57. 57conditions for equilibriumresultant torque must be zero
    resultant face must be zero
    closed triangle of vectors
  58. 58support forces from vectorssupport force is total vertical components of tension forces = total downward force (weight)
  59. 59unit of tensile stressPa or Nm2
  60. 60principle of momentsfor a body in stable equilibrium
    resultant torque is zero
    sum of clockwise = anticlockwise at a fixed point
  61. 61Car and trailer moving forwards affect on magnitude and direction on support force from tow barhorizontal component of f is created
    f increases in magnitude
    at an angle to the vertical towards the car
  62. 62whats the contact force of a truck going over a bridge of radius curvature rR= mg - mv2/r
  63. 63What happens to the contact force on a parcel in a van when it goes over a bridge at high speedWhen the speed is very high R is almost zero as it is in less contact with van floor. As v increases, centripetal force increases, and R decreases.
  64. 64when two springs are involved in a mass spring system whats k2k
  65. 65whats energy of a rechargeable cellE = Ivt
  66. 66Why is a capacitor not suitable for a cordless phoneCapacitor would have to be huge, voltage would be constantly decreasing, current not constant, short battery life
  67. 67How are energy losses minimised in high voltage transmission systemsHigh voltage transport to minimise current for same power, current causes heating, resistance in cables need to be low,
  68. 68interaction of the strong forcethe binding on neutrons and protons in the nucleus, the strong interaction
  69. 69Electrical energyE = VIt
  70. 70how can two lamps have the same power rating but different light intensity outputlight intensity is dependant on the efficiency of the bulb, the less efficient the more energy wasted and the lower the light intensity
  71. 71Why does doubling the mass not change gW = mg (F=ma), doubling m doubles w, the factor of two cancels and therefore g remains constant.
  72. 72why is measuring the g by free fall of card easier than a ballball will be more greatly affected by air resistance, decrease in acceleration, card unaffected. card more streamlined Difficultly of ball shape passing through light gate,
  73. 73Skateboarder down a slope, why does his acceleration decreasecomponent of weight causes acceleration down the slope. Increase speed down slope, air resistance and friction have greater resistive affect. As he moves further down, acceleration decreases/
  74. 74crate dropped from plane, why its velocity constantno horizontal force acting on crate, no acceleration, velocity is constant
  75. 75crate falling from plane if air resistance how will this affect maximum heightmaximum heigh decreased. Resistive vertical force of air resistance, downward acceleration decreased, slower fall.
  76. 76using energies to answer projectile questions1/2mv2 = mgh
    h is vertical displacement
    v is horizontal velocity
    assuming thermal energy is negligible
  77. 77angle of projection direction of velocity before hitting groundtan @ = F1/ F2
    tan -1 (f1/f2)
  78. 78direction of velocity of projectiletangent from path
  79. 79acceleration of ball changes when entering cylinder of liquidenters liquid, drag force due to viscosity or friction. Ball decelerates. as a decreases, the resistive force increases. Until they are equal. Acceleration is 0
  80. 80hookes lawthe force applied to stretch a material/wire/spring is proportional to its extension from its natural length up to a limit of proportionality.
  81. 81measuring the mass of a rock sample using a steel spring, standard mass and metre rulemeasure natural length with metre rule, work out extension, repeat with differing values of mass, plot mass against extension. mass = extension of spring supporting rock/ extension from supporting masses x M
  82. 82m = pALmass = density x cross sectional area x natural length (AL = volume)
  83. 83How does doubling youngs modulus of one spring affect its extension and cross sectional areayoungs doubled = extension doubled and cross sectional area doubled
  84. 84finding extension using youngsExtension = FxL / E x A
  85. 85Youngs modulusE = F X L / A X Extension (equations flipped for stress and strain )
  86. 86how to measure speed of a rising mass is constantrecord time taken to pass equal distances , times should be equal if speed is constant
  87. 87how to measure speed of a trolley before it strikes a block (down a ramp)piece of card of measured length on trolley
    light gate
    speed = length of trolley/ time obscured
  88. 88how to vary speed of trolley down a rampincrease starting height
    alter friction of slope
  89. 89why will a released ball (no resistive forces0 reach no higher than its starting release heightheight is constant
    GPE= MGH so h = GPE/MG
    no work done against resistive forces, initial GPE= final EK
  90. 90How to describe motion of a particle as the wave progressesif the wave moves to the right, you need to imagine it will go along the left and vice versa, describe these displacement changes instead of thinking it will go forwards. talk in terms of cycle time for more marks
  91. 91Why is it important to align the aerial of a tv in order to receive the strongest signalIt must be aligned in the same plane of polarisation of the radio waves, transmitted radio waves are often polarised.
  92. 92amplitude of a wavemaximum displacement of a vibrating particle from equilibrium position
  93. 93node and antinodenode = no displacement antinode = max displacement
  94. 94already polarised light passed through another polarising filter, rotated about 360 degrees.maxima at 0 and 180 and 360 degrees. minima at 90 and 270
    of varying intensity between these points (rising falling curve)
  95. 95use of polarisationpolaroid filter to reduce glare on windscreen and 3d glasses enhance entertainment
  96. 96conditions for a standing waveopposite wave direction
    similar amplitude
    same frequency
    same wavelength
    ( wave reflected back )
  97. 97how does increasing frequency increase oscillationsfrequency doubled oscillations in that length doubled ect
  98. 98standing wave fundamental modelength = 1/2 wavelength
    node at each end
    antinode in centre
  99. 99when deducing a particles identity if a particle is not a baryon or lepton what do we assumeits a meson
  100. 100when testing a diode what should we remembertake 6 values of v and i
    don't exceed 1 v
    keep current low in diode using protective resistor
  101. 101whats the equivalent to putting a diode in reverse biasreversing connections at the terminals
  102. 102how do we work out a peak to peak voltage from an rms valueRMS x square root 2
    x2
  103. 103why would an oscilloscope show a bright spot rather than a horizontal linethe time base was switched off
  104. 104why would momentum of air change as its going through an engine (with deflector plates)momentum and velocity are vectors. Even though the air is coming out at the same speed, its changing direction, its momentum is changing.
  105. 105if a material has a shallow or steep gradient on a youngs modulus graph what does this meansteep gradient, brittle sudden failure and large youngs
    shallow gradient, very ductile, a lot of weight before failure, large extension small youngs
  106. 106why is food rotated through a microwaveto continually change the positions of nodes and antinodes and allow even cooking
  107. 107stopping potentialv = w / q
    therefore stopping potential = ekmax/ electron charge
  108. 108increase frequency affect on stopping potentialincrease frequency increase photon energy increase ek max, charge of electron is same, so stopping potential increases
  109. 109why two photons for annihilationmomentum needs to be conserved
    two photons need to go in opposite directions
  110. 110symbol for electron0 e
    1
  111. 111Mev conversion1.6x10-16
  112. 112how can we identify b - decayis an electro released
    is an antineutrino released
    is no photon released
  113. 113what is muPA
    (mass per unit length)
  114. 114if you cover one slit of two how does the interference pattern changefewer maxima are observed
  115. 115how does spring constant affect frequency of oscillationshigher k = higher frequency
  116. 116what does a muon decay intoelectron, electron antineutrino, muon neutrino
  117. 117state on an electron in energy level 0free, released from atom
  118. 118why is there a high pd in discharge tubekeep electrons high speed and high energy to have enough energy to excite the gas atoms
  119. 119average power output of a batteryenergy it can supply / time its acting for
  120. 120path difference2wavelength
    difference between two D values (from slit to screen)
  121. 121why is it not zero at minima for interference patternsintensity decreases with distance, one wave may travel further than the other, they won't have the same amplitude causing some total amplitude after interference
  122. 122first second and third harmonic drawingremember to draw two loops to show its stationary
  123. 123what shows electrons have wave propertieselectrons dark rings in diffraction experiments

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A level Physics Flashcards on Things I have learnt from doing past papers , created by a m on 19/03/2018.
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