paper 2 physics

• transverse waves have perpendicular vibrations to the direction of energy transfer
• longitudinal waves have parallel vibrations to teh direction of energy transfer
• life cycle of a star:

  1. gravity pulls dust and gas in a nebula together to create a protostar.
  2. hydrogen nuclei undergo nuclear fusion to form helium nuclei.
  3. becomes a main sequence star (like our sun)
  4. eventually the hydrogen runs out and it becomes a red giant or red super giant.
• after being a red giant, small stars become a white dwarf, which eventually cools and becomes a black dwarf
• after being a red super giant, big stars explode in a supernova, which leaves behind a neutron star. if the star is big enough, it then becomes a black hole
• reflection: angle of incidence = angle of reflection
• specular reflection - all the light rays go a single direction
• diffuse reflection - light rays are scattered in different directions
• refraction: waves changing direction at a boundary, the speed of the wave changes depending on the density of the medium it is travelling through
• vectors have magnitude and direction
• force is a vector quantity
• non-contact forces include...

  • magnetic force
  • gravitational force
  • electrostatic force
• contact forces include...

  • friction
  • air resistance
  • tension
• gravitational force is a force of attraction between masses
• when a force moves an object through a distance, energy is transferred and work is done on the object
• an object is in equilibrium if the forces on it are balanced
• elastic deformation - an object is able to go back to its original shape and length once the force is removed
• inelastic deformation - an object cannot return back to its original shape and length once the force has been removed
• extension of a spring is directly proportional to force
• once a spring reaches the limit of proportionality, the force is too strong for it to be directly proportional, and the graph starts to curve
• a moment is the turning effect of a force (moment = force x distance)
• p waves are longitudinal
• s waves are transverse
• sound waves are transverse
• p waves can travel through solids and liquids, while s waves can only travel through solids
• microwaves and radio waves are used for communication
• x-rays and gamma rays are ionising and have high freqeuencies
• when light rays enter a denser medium, they bend towards the normal
• sound waves cannot travel through a vacuum
• motor effect - a current carrying wire in the presence of a magnetic field will experience a force
• infrared required practical:

  • leslie cube: matt black, shiny black, white, shiny metallic sides
  • infrared dector is more accurate than a thermometer because it has a higher resolution
  • hot water is added, matt black emits the most infrared radation
• atmospheric pressure - the total force of all the air particles constantly colliding with everything
• potential difference is generated when a wire experiences a change in magnetic field