Nova Lailatul Rizkiyah

arXiv2019

Minimal Tools for Accurately Measuring the Coefficient of Kinetic Friction

Measuring the coefficient of kinetic friction is much more difficult than that of the static counterpart. Here we report a simple method using minimal tool to accurately measuring the coefficient of kinetic friction. We employed an inclined plane, the tool for measuring time, and a protractor. This method is much simpler and cheaper than other methods reported by some authors previously. The results are consistent with the date reported elsewhere.

physics.ed-ph↗

arXiv2018

How a Snake Can Raise its Neck High although its Body is Very Soft. Similarity with a Thin Plastic Tube Filled with Air

The bodies of snakes, such as king cobras, are very soft so that it is nearly impossible for them to raise their heads higher than around one meter. By direct measurement, we were only possible to hold the body of a freshly killed cobra vertically at around 0.05 m. Here, for the first time it is reported that the king cobra can control the effective elastic modulus of its body so that it can raise its head up to several tens of centimeters. The effective elastic modulus is enhanced by increasing the pressure of air trapped inside the respiration channel, which is similar to increasing the stiffness of a thin plastic tube by filling it with air at pressure above atmospheric pressure. The neck height increases with the effective elastic modulus according to a scaling relationship. It was also simply proved that the peak of force or constriction pressure is proportional to the snakes diameter. This work may provide a physical foundation underlying the mechanical properties of slender animals.

physics.bio-ph↗