AS level OCR Physics

1. Prefix units 2. Uncertainties Adding or subtracting- Add the absolute uncertainties Multiplying or dividing- Add the percentage uncertainties Raising to a power- Multiply the percentage uncertainties by the power 3. Percentage un- certainty in the gradient uncertainty = ½(line of best fit - line of worst fit) Percentage uncertainty = uncertainty ÷ gradient of best fit line (× 100) 4. Speed Rate of change of distance 5. Displacement The distance an object has travelled in a given direction 6. Velocity Rate of change of displacement 7. Acceleration Rate of change of velocity 8. Scalars mass, time, temperature, speed, energy 9. Vectors displacement, force, velocity, acceleration 10. Velocity= u + at 11. Acceleration Change in velocity divided by time 12. Displacement= Average velocity × Time 13. Displacement= ut + ½at² 14. Velocity²= u² + 2as 15. 9.81 N / Kg Gravitational field strength 16. Displacement= ½gt² 17. Velocity= gt 18. Displacement= vt / 2 19. Velocity²= 2gs 20. Horizontal veloci- ty= V × Cos ¸ 21. Vertical velocity= V × Sin ¸ 22. Displacement Area under velocity-time graph 23. Time taken= Number of frames × (1 second / frame rate) 24. Stopping dis- tance= Thinking distance + Braking distance 25. Horizontal force= Force × Cos ¸ 26. Vertical force= Force × Sin ¸ 27. Inertia Resistance to a change in velocity 28. Pressure= h × Ád(ensity) × g 29. When the force isn't in the same direction as the movement W= F × x × Cos ¸ P= F × v × Cos ¸ 30. Power= Force × Velocity 31. K.E.= Work done 32. K.E.= Force × Displacement 33. K.E.= Mass × Acceleration × Displacement 34. Hooke's law Force is proportional to extension 35. K Force constant 36. K in series 1/K = 1/K1 + 1/K2 37. K in parallel K = K1 + K2 38. Tensile stress, Ã= Force / Area 39. Tensile strain, µ= Extension / Length 40. Work done= ½ × F × x 41. Force= K × x 42. Elastic potential energy= ½ × k × x² 43. Young modulus= Tensile stress / Tensile strain 44. Energy per unit volume= 45. Limit of propor- tionality ½ × Stress × Strain The graph is no longer a straight line The material stops obeying Hooke's law Returns to its original shape if stress were removed 46. Elastic limit The material behaves plastically No longer returns to its original state if stress were re- moved 47. Yield point Plastic deformation takes place with a constant or re- duced load The material stretches without any extra load 48. Conservation of momentum Momentum before = Momentum after 49. Elastic collision Momentum is conserved and kinetic energy is conserved 50. Inelastic collision Momentum is conserved but some kinetic energy is lost 51. Impulse (Ns) Change in momentum F × ”T 52. Newton's 1st law Force is needed to change velocity 53. Newton's 2nd law Force... Rate of change of momentum Change in momentum / Time 54. Newton's 3rd law Each force has an equal, opposite reaction force 55. Current Rate of flow of charge 56. One coulomb The amount of charge that passes in one second when the current is one ampere 57. Potential differ- ence Work done per unit charge 58. One volt The p.d. is one volt when you do one joule of work moving one coulomb of charge 1 V = 1 J / C 59. Current= Anev 60. One ohm If a p.d. of one volt makes a current of one amp flow through the component 61. Resistivity (Ohm metres) The resistance of a 1m length with a 1m² cross-sectional area 62. Resistivity= RA / L 63. Power= V × I 64. Work done= VI × T Power × Time 65. e.m.f, µ= V + v The total amount of work the battery does on each coulomb of charge 66. Resistance in se- ries Total R = R1+ R2 + R3 67. Resistance in par- allel 1/Total R = 1/R1 + 1/R2 + 1/R3 68. Potential divider (circuit with a volt- age source and V1 / V2 = R1 / R2 69. Intensity (W/m²) Power / Area 70. Intensity Intensity is the rate of flow of energy per unit area perpen- dicular to the direction of travel of the wave 71. Intensity is pro- portional to am- plitude squared Intensity Amplitude² 72. Polarised wave Oscillates in one direction 73. Refractive index= c / v 74. When a light n1 × sin ¸1 =n2 × sin ¸2 ray passes across Refractive index of first / second material- n1 and n2 a boundary be- tween two materi- als Angle of incidence / refraction- ¸1and ¸2 75. Sin C= 1 / n 76. Coherent Same wavelength and frequency with a fixed phase dif- ference Two coherent sources needed to get interference pat- terns 77. Constructive in- terference Path difference is a whole number of wavelengths Path difference = n» 78. Destructive inter- ference Path difference is an odd number of half wavelengths Path difference = (n + ½)» 79. Fringe spacing, x= »D / A 80. Stationary wave The superposition of two progressive waves with the same wavelength, moving in opposite directions 81. First harmonic Second harmonic Third harmonic One antinode- half a wavelength Two antinodes- one wavelength Three antinodes- one and a half wavelengths 82. Photon A quantum of EM radiation 83. E= hf = hc / » 84. Electronvolt The kinetic energy gained by an electron when it is accel- erated through a potential difference of one volt 1 eV = 1.6 × 10^-19 J 85. Photoelectric ef- fect 1) No photoelectrons are emitted if the radiation has a frequency below a certain value (threshold frequency) 2) The photoelectrons are emitted with a variety of kinetic energies ranging from zero to some maximum value. The value of maximum kinetic energy increases with frequen- cy and is unaffected by intensity 3) The number of photoelectrons emitted per second is proportional to intensity 86. Work function en- ergy, ¦ Energy needed to break metallic bonds 87. Planck constant, h 6.63 × 10^-34 Js 88. Threshold fre- quency, f= ¦ /h 89. For electrons to be released hf e¦ 90. Maximum kinetic energy hf= ¦ +max K.E. 91. de Broglie equa- tion »= h / p (momentum) 92. »for electrons ac- celerated in a vac- uum tube Same size as electromagnetic waves in the X-ray part of the spectrum 93. Archimedes' prin- ciple Upthrust = weight of fluid displaced