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'.]
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