Paper 1 physics

• Waves

  Transfer energy without transferring matter
• Types of waves

  • Transverse
  • Longitudinal
• Transverse waves


  Particles oscillate perpendicular to the direction of energy transfer
• Longitudinal waves


  Particles oscillate parallel to the direction of energy transfer, made up of compressions and rarefactions
• Standard wave

  • Displacement from midpoint (equilibrium) on y-axis
  • Time or distance on x-axis
  • Wavelength (Lambda)
  • Amplitude
• Time period

  Time taken for one complete wave to pass a point
• Frequency

  Number of complete waves passing a point every second
• Polarization

  Transverse waves can be polarized by a filter that only lets through waves oscillating in a particular direction
• Interference/Superposition


  When displacements of individual waves sum at each point, leading to constructive or destructive interference
• Harmonics

  • First harmonic: Wavelength = 2 * Length of string

  Second harmonic: Wavelength = Length of string
• Nodes


  Points of destructive interference, no energy transferred
• Anti-nodes


  Points of both constructive and destructive interference, energy transferred
• Coherence


  Waves have a constant phase difference
• Double slit pattern

  • Bright spots (maxima) where waves interfere constructively

  Dark spots (minima) where waves interfere destructively
• Path difference


  Difference in distance travelled by two interfering waves
• Phase difference


  Difference in the timing or position of two waves
• Single slit diffraction

  • Central maximum twice as large as other fringes, fringes fall away quickly
• Total internal reflection (TIR)

  Angle of incidence greater than critical angle, refractive index of first medium greater than second medium
• Average speed


  Distance / Time
• Displacement-time graph


  Gradient = Velocity
• Velocity-time graph


  Gradient = Acceleration

  Area under graph = Displacement
• Projectile motion

  • Horizontal motion uses constant speed, vertical motion uses SUVAT
• Newton's first law


  An object's motion is constant if no external force is acting on it
• Newton's third law


  For every action force, there is an equal and opposite reaction force
• Equilibrium


  No resultant force and no resultant moment
• Frictional forces


  Increase with speed
• Work done

  E = F * d, where F and d are parallel
• Stress


  Force / Area
• Strain


  Extension / Original length
• Stress-strain graph


  • Limit of proportionality

  Elastic limit

  Ultimate tensile stress
• Balanced forces


  Vector sum of all forces is zero
• Principle of moments

  Sum of clockwise moments = Sum of anticlockwise moments for equilibrium
• Scalars


  Quantities with magnitude only
• Vectors


  Quantities with both magnitude and direction
• Conservation of momentum


  Total momentum is conserved in the absence of external forces
• Braking distance


  Quadruples when speed doubles (due to KE being proportional to v^2)
• Elastic collisions


  Total kinetic energy is conserved
• Fundamental particles

  • Leptons (e.g. electron, positron, neutrinos)

  Hadrons (Baryons like proton, neutron, and Mesons like pions)
• Fundamental forces


  Electromagnetic (photon)

  Strong nuclear (pions)

  Weak (W+, W-, Z0)

  Gravity (graviton)
• Strong nuclear force


  Keeps nucleus together, has short range attraction and longer range repulsion