physics

• contact forces

  friction, air resistance, normal force, tension
• non-contact forces

  gravitational force, magnetic force, electrostatic force
• mass

  measure of the amount of matter in a body
• SI unit of mass

  kilogram
• electronic balance

  measures weight but calibrated to give readings in kg/g
• weight

  gravitational force acting on an object that has mass
• formula

  W=M x G

  where W is Weight (N) , M is Mass (Kg) and g (acceleration due to gravity/gravitational field strength)
• Is mass a scalar or vector?


  scalar
• Is weight a scalar or vector?


  vector
• gravitational field

  region in which a mass experiences a force due to gravitational attraction
• gravitational field

  any mass has a gravitational force

  direction: towards centre
• gravitational field strength

  gravitational force per unit mass placed at that point