8.4 Moving About
Increased access to transport
is a feature of todays 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 vehicles 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.
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 Newtons
- Vehicles do not travel typically
at a constant speed.
- An analysis of the external
forces on vehicles helps to understand the effects of
acceleration and deceleration.
- Moving vehicles have kinetic
energy and energy transformations are an important aspect
in understanding motion.
- Change of momentum relates
to the forces acting on the vehicle or the driver.
- Safety devices are utilised
to reduce the effects of changing momentum.
- The models applied to motion
and forces involving vehicles can be applied to a wide
variety of situations.
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national optical / infrared observatory. Includes an excellent
source of astronomical images taken by David Malin.
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