Physical science

• You need to learn about ancient Greek philosophy, cosmology and astronomy
• Celestial domain


  The domain of the heavens
• Terrestrial domain


  The domain of the Earth
• The Greeks started with what they can see
• Naked-eye observations available to the Greeks that led to the belief that the Earth must be round and not flat


  • Perihelion - when the planet is nearest to the Sun
  • Aphelion - when the planet is farthest from the Sun
• Ancient Greek Philosophers


  • Aristotle

  
• Modern Astronomy


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• Motion


  Movement or change in location of an object over time
• Galileo's 2 major contributions


  • Law of Falling Bodies
  • Law of Inertia - inertial motion of an object means that this motion can solely be changed by forces acting upon it

  
• Galileo discovered the law of inertia, but he did not name it
• 4 types of terrestrial motion


  • Alteration — simply chemical or physical changes
  • Vertical or natural local motion
  • Horizontal or violent motion
  • Celestial motion

  
• Natural motion


  In relation to the four-element model of Aristotle and their "natural position" in the Universe — Earth being at the middle of it, hence object made more of earth falls "faster" than those made more of fire or air

  
• Violent motion


  Related to the term "violent" being the state of motion that prevents the attainment of natural progression of motion: either frustrates or goes against natural motion. It is caused by external forces applied to the object. Aristotle taught that to maintain motion, an external force must continue to be exerted on the object

  
• Newton's First Law of Motion (Law of Inertia)


  An object at rest stays at rest, and an object in motion stays in motion at the same speed and direction, unless it experiences an unbalanced force

  
• Inertia


  • The tendency of all objects to resist a change in motion
  • The amount of inertia an object has depends on its mass – which is roughly the amount of material present in the object
  • Mass is proportional to its inertia. The more mass of an object, the more inertia!
• Force


  • A push or pull that causes an object to start moving or a moving object to stop
  • It may also speed up, slow down or change the direction of a moving object
  • Force can be defined as something that may cause change in the state of motion of an object
  • It is measured in Newtons (N)
  • Force is a vector quantity
  • 1 N (Newton) = 1 kg * m/s2

  
• Describing a Force


  • Magnitude: refers to the size or strength of the force. It is expressed in newton(N)
  • Direction: the direction the force is acting
• Balanced Forces


  • Forces act in pairs and can either be balanced or unbalanced
  • The sum of the forces acting upon an object is called net force, Fnet
  • If the sum of the forces equate to zero, they are considered balanced
• Balanced Forces


  • Fnet = Fn + Fg
  • Fnet = Fgirl + Fwall
  • Balanced forces do not cause change in motion
• Unbalanced Forces


  • If the net force is not equal to zero, the force is not balanced
  • An unbalanced force always causes a change in motion
  • When unbalanced forces act in opposite directions you can find the net force
  • Net force: Magnitude - the difference between the two forces
  • Direction - direction of the largest force