Agriculture Reference
In-Depth Information
In physics, we need to distinguish scalars from vectors. A scalar is a quantity
with a magnitude but no direction. A vector has both magnitude and direction.
A vector is a directed line segment in space that represents a force as well as a
velocity or a displacement.
It is not our goal to make every reader a physicist, only to remind ourselves that
there are no perpetual motion machines. A good design must never violate the
physical laws. Let us note some areas of sustainability that are heavily dependent
on physics. First, energy is often described as a system's capacity to do work, so
getting things done in the environment is really an expression of how efficiently
energy is transformed from one form to another. Energy and matter relationships
determine how things move in the environment. The physical movement of
contaminants follows the laws of physics. For example, after a contaminant is
released, physical processes go to work on transporting the contaminant and allow
for receptors (e.g., people, ecosystems) to be exposed. The same is true for any
substance, such as essential nutrients. Transport is one of two processes (the other is
transformation ) that determine a contaminant's or nutrient's fate in the environment.
Applications of Physics in Green Engineering
With the introduction of the physical laws, we can go a step further to discuss
physical relationships that bear on green engineering. We begin by revisiting
matter and energy. Every crucial environmental issue or problem can be rep-
resented, explained, and resolved using energy and matter fundamentals. How
contaminants are formed, how they change and move through the environment,
the diseases and problems they cause, and the types of treatment technologies
needed to eliminate them or reduce the exposure of people and ecosystems can
be seen through the prisms of energy and matter.
The relationship between energy and matter has only recently been character-
ized scientifically. Most simply, energy is the ability to do work; and work involves
motion. Kinetic energy is energy due to motion. The kinetic energy of a mass m
moving with velocity
v
is
1
2
E kinetic
=
2 m
v
(2.1)
Energy is also defined as the ability to cause change. Energy has a positional
aspect; that is, potential energy is the energy resulting from one body with respect
to another body. The potential energy of a mass m that is raised through a distance
h is
E potential =
mgh
(2.2)
where g is the acceleration due to gravity.
Search WWH ::




Custom Search