forces

• | vector

  • has a MAGNITUDE (size) & direction
  • eg: VELOCITY, distance, displacement, ACCELERATION, FORCE, momentum
  • represented by arrows, with their size/length representing the vector magnitude
• | scalar

  • has just MAGNITUDE
  • eg: SPEED, distance, TIME, MASS, energy
• | object interaction

  • force: push/pull that acts on an object due to the interaction with another object_
  • NON CONTACT: objects are physically separated
  • eg electrostatic: charges cause a force of attraction/repulsion
  • gravitational attraction: The mass creates a force of attraction
• | object interaction

  • contact: objects are physically touching
  • eg: friction: surfaces & their roughness = friction when moved in contact
• | gravity

  • all matter has a gravitational field & attracts all other matter
  • larger the mass = the stronger field = the greater the attraction
• | weight

  • WEIGHT: force exerted on a mass by the gravitational field, in Newtons
  • weight = mass (kg) × gravitational field strength
  • W = mg (9.8 on earth)
  • Measured by a force meter
  • Weighing scale measures the force you exert, and then divides by 10 to give mass
  • Same person on 2 different planets?
  • mass is same - gravitational field strength, g, at two planets will be different
  • their weight will be different on both
  • acceleration in free fall is bc gravity & is same as g
  • weight of object is considered to act at the object’s CENTRE OF MASS