The purpose of this publication is to bring attention to some physics problems whose answers seem to be paradoxical and, at first glance, do not agree with a limiting case check. Solving a problem on the motion of a system consisting of two masses and a spring, it is natural to examine the answer by considering a case when a spring constant is…

Pole vaulting, the aim of which is to jump over a crossbar with the help of a long flexible pole, is considered to be one of the most complicated and technically demanding motions in track and field athletics. Pole vault performance is basically influenced by the energy exchange between the vaulter and pole. It depends on the sprinting, jumping…

We describe a simple experiment about sliding friction of an object moving with non-constant speed along an inclined plane. This experiment can be used to study the entire dynamical process of force and motion in various ways, depending on the mathematical level of the students. We discuss how video measurement and analysis, and mathematical…

It is hard to observe relativistic effects in everyday life. However, table experiments using a mechanical transmission line for solitons may be an efficient and simple way to show effects such as Lorentz contraction in a classroom. A kink soliton is a deformation of a lattice of several dozen or more pendulums placed on a wire and connected by a…

The familiar system involving a uniform ladder sliding against a vertical wall and a horizontal floor is considered again. The floor is taken to be smooth and the wall to be possibly rough--a situation where no matter how large the static friction coefficient between the ladder and the wall, the ladder cannot lean at rest and must slide down.…

By means of a simple mathematical model developed by the authors, the apparent movement of the Sun can be studied for arbitrary latitudes. Using this model, it is easy to gain insight into various phenomena, such as the passage of the seasons, dependences of position and time of sunrise or sunset on a specific day of year, day duration for…

We present a case study of the physical principles necessary to model the high altitude parachute jump made by Colonel Joseph Kittinger, USAF, in 1960, in order to determine the maximum speed attained and to calculate whether this speed was sufficient to exceed the speed of sound at that altitude. There is considerable discrepancy in the value of…

An elementary analysis of a common textbook airplane problem is given, and then, as an illustrative example, the possibilities of this mechanism for animal navigation are briefly considered. (Author/MA)

Models the motion of a gymnast around the high bar first as swinging around a rigid rod, then more accurately when the rod is considered to be elastic. Also considers how the gymnast should best move his hips. (Author/ASK)