Forces

• what is a force ?

  a push or pull action on an object
• what is a contact force ?

  two objects must be physically touching for a force to be exerted e.g friction
• what is a non-contact force ?

  two objects do not have to be touching for a force to be exerted e.g gravity
• what does applying a force to an object cause ?

  • bend
  • stretch
  • compress
• what does it mean if an object is elastically deformed ?

  it will return to its original shape and size
• what happens to the energy when something is elastically deformed ?

  all energy is transferred to elastic energy stores
• what does gravity do ?

  • gives everything weight
  • attracts all masses
• what is mass ?


  the amount of stuff in an object
• what is weight ?

  a force exerted due to gravity
• what is distance ?

  • how far an object has moved
  • scalar quantity
• what is displacement ?

  • measure of distance and direction
  • Vector quantity
• what is speed ?

  • how fast an object is traveling
  • scalar quantity
• what is velocity ?

  • speed given a direction
  • Vector quantity
• what is resultant force ?

  overall force acting on an object
• how do you calculate resultant force ?

  • if forces act in the same direction add them
  • if the forces act in opposite directions subtract them
• what happens when force moves an object through a distance ?

  energy is transferred and work is done
• when is one joule of work done ?


  when a force of one Newton causes an object to move one meter
• what is acceleration ?

  the change in velocity in a certain amount of time
• what is the gradient on a distance time graph ?

  speed
• what is the flat line on a distance time graph ?

  stationary/ no movement
• what is the straight diagonal line on a distance time graph ?

  steady speed
• what is the curved line on a distance time graph ?

  acceleration
• what is the gradient on a velocity time graph ?

  acceleration
• what is the area under the line on a velocity time graph ?

  distance
• what is the flat line on a velocity time graph ?

  steady speed
• what is the straight diagonal line on a velocity time graph ?

  acceleration/ deceleration
• what is the curve on a velocity time graph ?

  increasing acceleration
• what is terminal velocity ?

  when the upwards and downwards force is equel (0 resultant force)
• what is inertia ?


  these tendency for motion to remain unchanged
• describe momentum

  • in a closed system momentum is equal before and after an event
  • it is a vector quantity
  • mass and velocity are directly proportional to momentum
• what is newtons first law ?

  if resultant force on an object is zero the object will remain stationary
• what is newtons second law ?

  acceleration and force are directly proportional
• what is newtons third law ?

  when two objects interact the forces they exert are equal and opposite
• what is the terminal velocity skydiver example ?

  • when first out of plane the only force acting is weight
  • when he starts falling air resistance acts, the faster he falls the greater the air resistance
  • air resistance and weight become equal and terminal velocity is reached
  • once parachute opens air resistance increases and sky duvet v rises a little
  • steps repeat again until terminal velocity is reached
• what can effect braking distance ?

  • speed
  • weather
  • quality of tires
  • quality of brakes
• what can effect thinking distance ?

  • speed
  • reaction time
• what is reaction time ?


  length of time taken for a person to respond to something
• what does breaking rely on ?


  the friction between the brakes and wheels