Physics

• define vector


  quantise with magnitude and direction
• List some vectors (6)

  force, velocity, displacement, weight, acceleration, momentum
• define scalar


  quantities with magnitude but no direction
• list some scalar quantities (6)

  speed, distance, mass, energy, temperature, time
• define velocity


  speed in a given direction
• distance =


  s x t
• walking speed =


  1.4m/s
• running speed =


  3m/s
• cycling speed=


  5.5m/s
• cars in towns speed

  13m/s
• cars on motorway speed

  31m/s
• trains speed


  (up to) 55m/s
• wind speed


  5-20m/s
• speed of sound in air

  340m/s
• define acceleration


  change in velocity in a certain length of time
• acceleration =


  (v-u)/t
• what causes acceleration of all objects in freefall to be equal

  gravity
• accelerate due to gravity =


  10m/s/s
• uniform acceleration =


  v2-u2=2xaxx
• gradient on distance time graph =

  speed
• average speed =


  total distance/time
• gradient of velocity time graph =

  acceleration
• area under velocity/time graph =

  distance
• Newton's first law


  a force is needed to change motion
• If the resultant force on a stationary object is zero

  object will remain stationary
• if resultant force on an moving object is zero

  it will continue to move at the same speed
• five forms of an acceleration


  starting, stopping, speeding up, slowing down, changing direction
• the larger the resultant force on an object


  the more it accelerates
• relationship between force and acceleration

  directly proportional
• force =


  massxacceleration
• Newton's second law


  f=mxa
• safety features in cars designed to increase collision time to reduce force are

  seatbelt, airbags, crumple zones
• how does a vehicle skid (brakes)

  brakes do work on wheels, energy transferred from kinetic to thermal stores, brakes overheat
• define mass


  amount of stuff in an object
• define weight


  the force acting on an object due to gravity (caused by the gravitational field)
• unit of weight


  newtons
• what is the single point where the force of weight acts on an object called

  centre of mass
• weight =


  mass x gravitational field strength
• If an object is travelling in a circle

  constantly changing direction and velocity so must be accelerating
• name of the force which keeps something moving in a circle

  centripetal force