EXPERIMENTAL: AN INVESTIGATION INTO ELASTIC POTENTIAL ENERGY

Introduction
Strictly speaking, there are only two forms of energy: namely, kinetic
and potential.  However, both forms can be conveniently divided into
various types; e.g., chemical, elastic, gravitational, and nuclear are
all types of potential energy.

Elastic potential energy is stored in a number of substances (e.g., in
compressed springs, stretched rubber, and compressed gases), and then
transduced into kinetic energy (e.g., in clockwork toys, trampolines,
and combustion engines); as with all energy transductions, there is
also a transfer of 'low-grade' heat energy to the surroundings.

Despite the availability of well-established equations to measure
energy (e.g., elastic potential energy = 0.5 × force × extension), it
is often necessary to determine new relationships by experiment ...

Using a combination of experimental and graphical methods, you are
required to investigate the relationship between the extension (E) of
a rubber band and the distance (D) moved by a missile; in particular,
to determine which of the following relationships is most valid:
D = k × E;       D = k × E-1;       D = k × E0.5;       D = k × E2

Notes and Extension Work
1.  You are provided with a block of wood, callipers, drawing pins,
graph paper, 'missiles', newtonmeter, rubber bands, and rulers. In
addition, you may use - within reason - other suitable apparatus.

2.  The proposed plan of your investigation should be presented in
detail; this plan will almost certainly need to be modified as the
investigation proceeds, because initial attempts to obtain reproducible
results are usually unsuccessful (... 'patience is a virtue' ...).

3.  [Extension: To determine the most valid relationship will involve
keeping all but one of the independent variables constant. Investigate
the effect of another independent variable on the value of 'k'.]

Dr. R. Peters                  Next                      Contents' List