P5

• Scalar quantities


  Physical quantities that only have a magnitude or size
• Vector quantities


  Physical quantities that have both a magnitude and a direction
• Scalar and vector quantities are treated differently in calculations
• Adding scalars


  Sum the values together
• Subtracting scalars


  Subtract one value from another
• Scalar quantities


  Physical quantities that have magnitude (size) but no associated direction
• Vector quantities


  Physical quantities that have both magnitude (size) and an associated direction
• Vector quantities


  • Force (20 newtons to the left)
  • Displacement (50 kilometres east)
  • Velocity (11 metres per second upwards)
  • Acceleration (9.8 metres per second squared downwards)
  • Momentum (250 kilogram metres per second south west)
• The direction of a vector can be given in a written description, or drawn as an arrow
• The length of an arrow represents the magnitude of the quantity
• Scalar quantities


  Physical quantities that have magnitude (size) but no direction
• Vector quantities


  Physical quantities that have both magnitude (size) and direction
• Calculations involving forces


  1. Determine the resultant force

  2. Add forces acting in the same direction

  3. Subtract forces acting in opposite directions
• Resultant force


  The single force that could replace all the forces acting on an object, found by adding these together
• If all the forces are balanced

  The resultant force is zero
• Two forces acting in the same direction


  • 3 newtons (N) and 2 N, act to the right
  • Resultant force is 5 N to the right
• Two forces acting in opposite directions


  • A force of 5 N acts to the right, and a force of 3 N act to the left
  • Resultant force is 2 N to the right
• Free body diagrams


  Used to describe situations where several forces act on an object
• Vector diagrams


  Used to resolve (break down) a single force into two forces acting at right angles to each other
• Contact forces


  Forces exerted between two objects when they are touching
• Contact forces


  • A push or a pull
  • The unit of force is the newton (N)
• Reaction force


  Force exerted in the opposite direction to an action force
• Tension


  Pulling force exerted by each end of an object such as a string or rope
• Friction


  A force that opposes or prevents movement and converts kinetic energy into heat
• Air resistance


  A force of friction produced when an object moves through the air
• When a contact force acts between two objects, both objects experience the same size force, but in opposite directions
• This is Newton's Third Law of Motion
• Forces


  Responsible for all the interactions between particles and objects
• Types of forces


  • Contact forces
  • Non-contact forces
• Non-contact forces


  Forces that act between two objects that are not physically touching each other
• Magnetic force


  Force experienced by any magnetic material in a magnetic field
• Opposite magnetic poles (N - S or S - N)


  Attract each other
• Like magnetic poles (N - N or S - S)


  Repel each other
• Electrostatic force


  Force experienced by any charged particle in an electric field
• Opposite charges (+ and -)


  Attract each other
• Like charges (- and -, or + and +)


  Repel each other
• Gravitational force


  Force experienced by any mass in a gravitational field
• Masses are attracted towards each other by gravitational force
• Gravity


  One of the most important forces in the universe
• Gravitational field


  A field that exerts a force on objects with mass