Physics

• Hearing


  1. The diaphragm vibrates

  2. The vibrations are transmitted through the ossicles

  3. The vibrations are detected by the hair cells in the cochlea

  4. The hair cells convert the vibrations into electrical signals

  5. The electrical signals are sent to the brain
• Ossicles


  The hammer, anvil and stirrup bones in the middle ear
• Our hearing range is 20Hz-20kHz
• Noise


  Any unwanted sound
• Noise


  • Can lead to deafness, tinnitus, and other health issues
  • Can be reduced by using ear protection, soundproofing, and isolating machinery
• Wavelength


  The distance from one point on a wave to the same point on the next wave
• Frequency


  The number of waves that pass a given point per second
• Amplitude


  The height of the wave from the midpoint to the peak or trough
• Decibel (dB)


  A measure of how loud a sound wave is
• Types of waves


  • Mechanical
  • Electromagnetic
  • Longitudinal
• The speed of sound in air at 20°C is 343 m/s
• Types of energy


  • Thermal
  • Magnetic
  • Electrostatic
  • Gravitational
  • Elastic
• Energy transfer


  When energy moves from one place to another through an energy pathway
• Conduction


  Transfer of heat through direct contact between particles
• Convection


  Transfer of heat by the movement of a fluid (liquid or gas)
• Radiation


  Transfer of heat through electromagnetic waves
• Insulators


  • Slow down the transfer of heat
  • Trapped air is a good insulator
• Shiny surfaces


  • Better at reflecting light
  • White/bright surfaces are good at reflecting light
• Voltage


  The push given to electrons in a circuit
• Current


  The flow of electrons or charge in a circuit
• Electrical resistance


  The opposition to the flow of electric current
• Variable resistors


  • Can be used to alter current flow in a circuit
  • High currents can cause fire risks
• The nearest objects you can see without a telescope are artificial satellites and the International Space Station
• Comets are huge snowballs that orbit the Sun
• Meteors are bits of dust or rock that burn up as they pass through the Earth's atmosphere
• The Milky Way is the galaxy that contains our solar system and most of the stars we see in the night sky
• Planets in the solar system

  • Inner planets (terrestrial): Mercury, Venus, Earth, Mars
  • Outer planets (gas giants): Jupiter, Saturn, Uranus, Neptune
• Inner planets


  • Made of rock
  • Have very different conditions
• Outer planets


  • Mainly made of hydrogen and helium
  • Much bigger than inner planets
• Many planets have moons orbiting them, with Saturn having the most at over 60
• The asteroid belt is a region between the orbits of Mars and Jupiter containing thousands of pieces of rock
• Pluto was reclassified from a planet to a dwarf planet in 2006
• The Kuiper Belt is a region beyond Pluto's orbit where most comets originate
• Earth


  • Spins on its axis, causing day and night
  • Orbits the Sun once per year, causing the seasons
• The Earth's axis is tilted at 23.4 degrees, causing the seasons
• In summer, the Sun's rays spread over a smaller area, making it hotter, and the days are longer
• At the North and South Poles, there are periods of 24-hour daylight (midnight sun) and 24-hour darkness (polar night) due to the tilt of the Earth's axis
• Energy stores


  • Electrical
  • Elastic - potential
  • Nuclear
  • Chemical
  • Gravitational Potential
  • heat
  • kinetic
• Energy types


  • Electrical
  • Elastic - potential
  • Nuclear
  • Chemical
  • Gravitational Potential
  • heat
  • kinetic
• Energy transfers


  1. Mechanically (when a force acts and something moves)

  2. Electrically (through a flow of charge)

  3. by heating (because of a temperature difference – from hotter to colder areas)

  4. by radiation (a wave such as light, microwaves or sound)