8.4 Moving About

John Storey
School of Physics - UNSW, 
November 1999.

Contextual Outline

Increased access to transport is a feature of today’s society. Most people access some form of transport for travel to and from school or work and for leisure outings at weekends or on holidays. When describing journeys that they may have taken in buses or trains, they usually do so in terms of time or their starting point and their destination. When describing trip they may have taken in planes or cars, they normally use the time it takes, distance covered or the speed of the vehicle as their reference points. While the distance and speed are fundamental to the understanding of kinematics and dynamics, very few people consider a trip in terms of energy, force or the momentum associated with a vehicle, even at low or moderate speeds.

The faster a vehicle is travelling, the further it will go before it is able to stop. Major damage can be done to other vehicles and to the human body, even at low speeds. This is because during a collision some or all of the vehicle’s kinetic energy is dissipated through the vehicle and the object with which it collides. Further, the materials from which vehicles are constructed do not deform or bend as easily as the human body. Technological advances and systematic study of vehicle crashes have increased understanding of the interactions involved, the potential resultant damage and possible ways of reducing the effects of collisions. There are many safety devices now installed in or on vehicles, including seat belts and air bags. Modern road design takes into account ways in which vehicles can be forced to reduce their speed by strategically placing speed humps and dampeners.


Assumed Knowledge

From Sciences Stage 4-5 syllabus.


  • 5.6.2a Describe qualitatively the relationship between force, mass and acceleration.
  • 5.6.2b Explain qualitatively the relationship between distance, speed and time.
  • 5.6.2c Relate qualitatively acceleration to change in speed and/or direction as a result of a net force.
  • 5.6.2d Analyse qualitatively common situations involving motion in terms of Newton’s Laws.



  1. Vehicles do not travel typically at a constant speed.
  2. An analysis of the external forces on vehicles helps to understand the effects of acceleration and deceleration.
  3. Moving vehicles have kinetic energy and energy transformations are an important aspect in understanding motion.
  4. Change of momentum relates to the forces acting on the vehicle or the driver.
  5. Safety devices are utilised to reduce the effects of changing momentum.
  6. The models applied to motion and forces involving vehicles can be applied to a wide variety of situations.


(a) Institutions

Board of Studies, New South Wales

Department of Astrophysics, University of New South Wales

  • http://www.phys.unsw.edu.au/astro.html
    One of Australia’s leading university research groups in astronomy, with particular strengths in star formation, cosmology, infrared astronomy, millimetre-wave astronomy and Antarctic astronomy.

School of Physics, University of New South Wales

  • http://www.phys.unsw.edu.au/
    One of Australia’s premier physics groups, undertaking a wide range of research activities, including condensed matter physics, biophysics, environmental physics and astrophysics.

Astronomical Society of Australia

Australian Institute of Physics

Anglo Australian Observatory

  • http://www.aao.gov.au/
    Australia’s national optical / infrared observatory. Includes an excellent source of astronomical images taken by David Malin.

Australia Telescope National Facility

Treasure Trove of Science

  • http://www.treasure-troves.com
    Eric Weissen’s encyclopaedia of science, with particular volumes for physics and for astronomy. A comprehensive reference source.


Further Information



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