physics double

• newtons 3rd law


  if body A exerts a force on body B then body B exerts an equal and opposite force on body A
• Newtons 1st law


  A body will remain at rest or in uniform motion in a straight line unless acted upon by an external force
• half life 


  the time taken for a radioactive isotopes mass or activity to decay by half
• order of planets

  mercury

  venus

  earth

  mars

  jupiter

  saturn

  uranus

  neptune
• life cycle of a small start

  protostar

  main sequence star

  red giant

  white dwarf
• life cycle of a large star

  protostar

  main sequence star

  red super giant

  super nova

  neutron star OR black hole
• forces and reactions in a main sequence star

  forces are balanced

  gravity = gas pressure

  hydrogen fuses into helium
• forces in a main red giant/ super giant

  forces are unbalanced

  gas pressure is greater than gravity

  no hydrogen

  helium fuses into heavier elements
• forces in a main white dwarf/neutron star/black hole

  no reactions because there is no gas

  gravity is higher than gas pressure
• factors affecting thinking distance

  drugs

  alcohol

  tiredness

  distractions

  age
• factors affecting breaking distance

  tyres

  road conditions

  weather

  break conditions
• stopping distance is breaking distance + thinking distance
• as speed doubles thinking distances doubles and breaking distance quadruples
• how is radioactive waste disposed of?

  stored in concrete containers deep under the sea
• why are repeat readings taken?

  reduce anomalies in the results

  improve confidence in results
• alpha decay


  helium nucleus

  very ionising (2+)

  low penetrating

  blocked by skin and paper
• beta decay

  fast moving electron

  less ionising (1-)

  medium penetrating

  blocked by aluminium
• gamma decay

  EM wave

  not ionising (no charge)

  very high penetrating

  blocked by thick lead or concrete
• terminal velocity 


  the maximum speed an object can reach when forces are balanced
• safety features in a car

  seat belts

  crumple zones

  air bags
• how to make cars more efficient

  stop start systems to reduce waste while stationary

  lighter materials to reduce the mass of the car

  more streamlined designs as it is more aerodynamic to reduce less air resistance

  correctly inflated tyres to reduce rolling resistance
• when a force acts on a body work is done. work is a measure of the energy transferred. it is always measured in Joules (J)

  work = force x distance moved
• when calculating energy we use:

  kinetic energy= mass x velocity2 •/• 2

  gravitational potential energy = mass x gravitational field strength x change in height

  energy stored in a spring = area under force extension graph