P5 - Forces

• vectors have magnitude and direction
• vector quantities

  • force
  • velocity
  • displacement
  • acceleration
  • momentum
• scalar quantities

  • speed
  • distance
  • mass
  • temperature
  • time
• contact force


  when two objects have to be touching for a force to act
• non-contact forces

  when objects do not have to be touching for the force to act
• contact forces

  • friction
  • air resistance
  • tension
• non-contact forces

  • magnetic
  • gravitational
  • electrostatic
• the sun and the earth are attracted to each other by a gravitational force.
• a chair exerts a force on the ground whilst the ground pushes back at the chair with the same Force. equal but opposite forces are felt by both the chair and the ground
• the sun and the earth are attracted to each other by the gravitational force. this is a non-contact force. an equal but opposite force of attraction is felt by both the sun and the earth
• mass


  amount of matter in an object
• weight


  the force acting on an object due to gravity
• weight = mass x gravitational field strength
• resultant force

  overall force on a point or object
• when a force moves an object through a distance, energy is transferred and work is done on the object
• Work done = force x distance
• equilibrium

  forces are balanced
• Force (N) = spring constant (N/m) x extension (m)
• moment

  turning effect of a force
• Moment = Force x perpendicular distance from the pivot
• levers


  increase the distance which means the force needed decreases making it easier to turn
• gears transmit rotational effects
• pressure = force/area
• pressure is measured in pascals
• pressure = height x density (kg/m$^3$) x gravitational field strength
• objects in fluids experience upthrust
• an object floats if upthrust = weight
• atmospheric pressure decreases with height
• acceleration 


  how quickly you speed up
• acceleration = change in velocity / time
• s - distance

  u - initial velocity

  v - final velocity

  a - acceleration

  t - time
• v$^2$ - u$^2$ = 2as
• terminal velocity 


  maximum speed
• newtons first law

  every object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• Newtons second law

  F = ma

  Resultant = mass x acceleration
• inertia is the tendency for motion to remain unchanged
• Newtons 3rd law

  when two objects interact, the forces they exert on each other are equal and opposite
• stopping distance = thinking distance + breaking distance
• thinking speed is affected by

  • speed
  • reaction time
• breaking speed is affected by

  • speed
  • weather
  • condition of tyres
  • condition of breaks