physics

• newton’s first law

  an object in motion will stay in motion as long as the forces acting in it remain balanced.
• newton’s second law

  acceleration of the object is directly proportional to the force acting on the object and inversely proportional to the mass of the object
• weight

  the force that an object experiences due to its mass and the size of the gravitational field it is in. it is measured in Newtons (N)
• Core Practical: force and acceleration

  • set up apparatus
  • set up light gates to take velocity and time recordings
  • record velocity and time values for different masses of trolley
  • work out acceleration by dividing difference in velocity by time taken to pass between both gates
• Circular motion:

  • an object moving in a circle with have a constant speed but a changing velocity because the direction will be constantly changing
  • for circular motion to occur there must be a force acting inwards along the radius of the circle. this is called a centripetal force
  • the object move at right angles to this force
• newton’s third law


  for every action there is an equal and opposite reaction
• energy resources:

  Renewable:

  • bio-fuels: animal or plant matter used to produce energy
  • hydroelectricity: generated from water behind a da, flowing down a pipe and turning a turbine to generate electricity
  • wind turbines: use kinetic energy from the wind to generate electricity
  • tidal power: use the rise and fall of tides to generate electricity
  • solar panels: convert solar energy from the Sun into electricity

  Non-renewable:

  • nuclear fuels: used to generate electricity and power spacecraft
  • fossil fuels: coal, oil, natural gas
• Waves:

  • frequency: number of waves passing a point each second
  • speed: measured in m/s
  • wavelength: distance between corresponding points of two consecutive waves
  • amplitude: amount of energy transferred by a wave
  • period: time taken for one wavelength to pass a point- also 1/frequency
• Longitudinal waves:

  • sound waves, seismic P waves
  • particles move back and forth along the same direction that the wave is travelling
• Transverse waves:

  • water surface, electromagnetic, seismic S waves
  • particles move at right angles to the direction the wave is travelling
• Calculating the speed of sound in air:

  Method 1:

  1. measure distance from the source of the sound to reflecting surface (wall)
  2. measure time interval between original sound being produced and echo being heard
  3. use speed = distance/time

  Method 2:

  1. set up microphones at different distances in a straight line from a loudspeaker. set frequency of sound from loudspeaker to a known, audible value
  2. display the two waveforms on oscilloscope. measure distance between microphones
  3. move microphones apart so waveforms move apart by one wavelength
  4. use wave speed= frequency x wavelength
• • whenever a wave reaches the boundary between two materials, they can be: reflected, refracted, transmitted or absorbed.
  • water molecules absorb microwave and infrared wavelength but transmit radio waves which have longer wavelengths
  • infrared radiation is transmitted by a black plastic bag but visible rays are not, they are absorbed
• Refraction: The bending of light as it passes from one medium to another.

  • sound waves travel slower in cooler, denser air than in warmer, less dense air
  • water waves travel faster in deep water than in shallow water. they can also change direction
  • light waves can slow down and change direction when they pass from air to glass
• Electromagnetic spectrum:

  • transverse waves
  • all travel at the same speed- 3 x 10 ^ 8
  • transfer energy to the absorber

  Shortest ---> longest

  Gamma, x-ray, ultraviolet, visible, infrared, microwaves, radio waves

  Visible light spectrum: rainbow

  Shortest= purple, longest= red
• Core practical: refraction

  1. place rectangular block on the A3 paper and draw around it with a sharp pencil
  2. draw the normal line at right angles to the side of the block towards which the light ray will be shone
  3. using the protractor and pencil, mark on the paper angles of incidence 0-80 in 10 degree intervals
  4. starting with the 0 degree angle, direct the light ray towards the block and mark its exit point from the block with a sharp pencil dot
  5. Remove glass box and join the dot to the point of incidence by drawing a straight line. measure and record this as the angle of refraction.
• an electron will move from a lower to a higher orbit if it absorbs electromagnetic radiation.

  an electron will move from a higher to a lower orbit if it emits electromagnetic radiation.
• atoms become positive ions when they lose electrons. this can happen when they:

  • absorb electromagnetic radiation of enough energy for them to escape the pull of the nucleus (UV, X-rays, gamma rays)
  • are hit by a particle such as an alpha or beta particle
• B- decay:

  • a neutron in the nucleus of an unstable atom decays to become a proton and an electron.
  • the proton stays in the nucleus but the electron, which is the B- particle, is emitted from the nucleus at a high speed
• B+ decay:

  • a proton in the nucleus decays to become a neutron and a positron.
  • the positron, which is the B+ particle, is emitted from the nucleus at a very high speed, carrying away a positive charge and a very small amount of the nuclear mass
• Dangers of electromagnetic waves:

  • X-rays and gamma rays: can cause mutations to the DNA in cells in the body, which could kill cells or cause cancer
  • UV: can cause sunburn, skin cancer and damage to the eyes
  • Infared: transfers thermal energy which can cause skin burns
  • Microwaves: can heat water inside our bodies, which can damage/ kill them.
• Uses of electromagnetic waves:

  • Gamma rays: treat and detect cancer; sterilise food and medical equipment
  • X-rays: look inside objects and bodies; airport scanners
  • UV: fluorescent lamps; detect forged banknotes; disinfect water
  • Infared: cooking; thermal energy; optical fibres; burglar alarms; short-range communication
  • Microwaves: mobile phones; satellite transmissions; cooking
  • Radio waves: broadcasting radio and TV shows; communicate with ships, aeroplanes, satellites etc.
• inertial mass: measure of how difficult it is to change the velocity of an object