The statics of fluids may seem simple at first but often poses problems for students when it comes to applying it to concrete cases. Despite its relatively simple laws, some subtleties, mainly related to the elastic characteristics of a fluid, must be noted. This elasticity allows the pressure exerted in a part of the fluid to propagate in its…

A classical mechanical structure with an internal degree of freedom is shown to reflect off a potential well. Such behavior is impossible for point-like or rigid classical particles. This numerical study provides insight for students studying internal energy and degrees of freedom.

A key concept in current fluid dynamics and its applications to biology and technology is a phenomenon known as wetting. Wetting is familiar from everyday life and is simply the ability of a liquid to stay in contact with a solid surface. The wettability depends on the properties of the liquid and the solid and can be characterized by the static…

The Young-Laplace (Y-L) equation relates the pressure difference across the interface of two fluids (such as air and water) to the curvature of the interface. The pressure rises on crossing a convex interface such as a rain drop and falls on crossing a concave interface such as the meniscus of water in a glass capillary. The relation between…

Although the old problem of rotating liquid is described and solved in many textbooks and articles, the story still remains interesting. Intuitive understanding of the equipotential spatial surfaces is very difficult. This article is an attempt to present Newton's rotating tank in the light of the law of conservation of energy.

A good paradox has the viewer confused, but the best paradoxes lead the viewer to try to understand what is happening. One of the author's favorites is the hydrostatic paradox, in which a short and slender column of water supports a relatively enormous weight. He describes the paradox using an illustration of a student who weighs 60 points stands…

The laser pointer has been widely used to demonstrate some simple optics phenomena, like reflection, refraction, total reflection, and diffraction. However, the rays of laser light cannot be seen in the air because the scattered light is too weak. Many physics teachers use milk or smoke to visualize rays of laser light in physics labs, but it is…

Water rockets can be used in a variety of ways, from schools to planetariums, with very young kids or adults. We propose here simple forms to work with water rockets, going one step further than a simple launch. A smartphone can be used to film the launch and analyze its motion with video analysis or it can even be attached to the rocket, using…

Newton's laws are a ubiquitous topic in introductory physics instruction. One common problem involves asking what will happen if you stick your finger into a cup of water sitting on a scale. A way to solve the problem would be to first recognize that the water exerts a buoyant force upward on the finger, which students can recognize as being the…

Apparatus catalogues of the first half of the 20th century contain a number of clever and simple devices for measuring the index of refraction of a liquid. In some cases students can put together one of these pieces of apparatus and then make their own measurements. The Gilley board was one of the devices that caught my eye, and I would like to…

The physical problem of a body of water in a tank that drains through a hole in the base is a classical problem that has been studied since at least the time of Torricelli. To fixate this in a student's mind, one could ask them to visualize a bathtub that is being drained through the plughole or a bottle being drained through a tap. This problem…

Students may have some confusion understanding certain physical concepts and principles because of their abstract nature. Using analogies is one of the useful methods to help them more easily grasp abstract concepts to promote conceptual understanding. Bilaloglu classified analogies in four groups: (a) simple analogies, (b) storified analogies,…

The debate over the mechanisms responsible for the flow rates of simple tube siphons has received much attention in the physics education and general physics literature in the past decade. Particularly with regard to the driving mechanism for water siphons, some suggested explanations emphasize contributions, or lack thereof, from the atmospheric…

The non-SI unit sverdrup, named to honor Norwegian oceanographer and meteorologist Harald Ulrik Sverdrup (1888-1957), is adopted for quantifying large-scale volume transport by oceanographers, meteorologists, and atmospheric physicists. The sverdrup is used to appraise the volumetric rate of evaporation, precipitation, runoff, transport of ocean…

One of the most popular demonstration experiments pertaining to Bernoulli's principle is the production of a water spray by using a vertical plastic straw immersed in a glass of water and a horizontal straw to blow air towards the top edge of the vertical one. A more general version of this phenomenon, appearing also in school physics problems, is…