Results
Conclusion
It was hypothesized that the combination of expanded polypropylene (EPP) foam and Sorbothane would yield the lowest mean acceleration. However, the lowest mean acceleration was found by using the combination of EPP and memory foam. Therefore, the hypothesis of this experiment was rejected.
Data Analysis
Results showed that the combination of EPP and memory foam yielded the lowest average acceleration, which was not hypothesized. However, a statistical test was conducted in order to see if there was any significant difference among the four combination's mean accelerations. The results of this test showed that there was no statistically significant difference between any of the foam combinations' acceleration. Test statistic F of 0.72 gave a Pvalue of 0.54, this shows that there was about a 54% probability that these results happened by chance alone, given that the mean acceleration of the groups were assumed to be equal.
Impulse
Impulse is a change in momentum and it is the product of force and the time the force is applied. When the helmet was struck, the initial shock wave of the force traveled through the shell of the helmet, into the first layer, then the second layer, then reached the head. The first layer absorbs much of the impact due to the thickness and composition of the foam. The second layer, softer and more flexible foam, served as the inner layer of the helmet. Since these foams are able to compress, the time of the applied force is increased, and therefore the force experienced is significantly less than if there was no helmet at all.
Improvements
To further improve this experiment, thicker materials can be used to make the head fit perfectly into the helmet. The same size rubber bands or even a whole different spring loading system could be used to reduce any bias that could occur. For future research, different materials can be tested. Also different locations of impact and how they affect the acceleration of the head could be tested. This will allow helmet designers to figure out where to put the most protection inside the helmet.