dynamics I : mass and weight

• 2 types of force:

  • contact

  eg. friction, air resistance, normal force, tension

  • non-contact

  eg. magnetic force, gravitational force, electrostatic force
• contact forces exist when 2 objects are in contact
• mass:

  • measure of the amount of matter in an object (does not change with its location or shape)
  • SI unit is kilogram (Kg)
  • is a scalar quantity
• weight:

  • gravitational force acting on an object that has mass
  • SI unit is Newton (N)
  • is a vector quantity
  • direction is downwards i.e towards the earth
• gravitational field:

  • region where mass experiences a force due to gravity
  • strongest at Earth's surface