chapter 3

• force


  push and pull due to interactions between objects to explain changes in motion

  can be classified into contact and non-contact forces
• gravitational force

  the pull exerted by Earth's gravity on any object
• electrostatic force

  the attractive or repulsive forces between electric charges
• magnetic force

  attractive or repulsive force between magnets
• friction

  force that opposes or tends to oppose motion between surfaces in contact
• air resistance


  frictional force exerted by air that opposes the motion of moving objects
• normal force


  the push exerted by a surface on an object pressing it, push is always perpendicular to the surface
• tension

  pull exerted by a stretched string, spring or rope on an object attached to it
• mass

  a property that does not change with its location or shape, dependent on the number and composition of atoms and molecules that make up the body
• gravitational force due to gravitational field strength

  gravitational force is the stronger at the surface of the Earth

  gravitational force weakens as it gets further away from the surface of Earth due to decreasing gravitational field strength
• weight

  dependent on the gravitational field strength at a certain location

  weight of an object is directly proportional to its mass
• properties of mass


  amount of matter

  scalar quantity

  si unit is kilogram

  independent of gravitational field strength

  measured with a beam balance or calibrated electronic balance
• properties of weight

  gravitational force

  vector quantity

  si unit is newton

  dependent on the gravitational field strength

  measured with spring balance