The falling raindrop, revisited

The weight of a falling chain, revisited

A vertically hanging chain is released from rest and falls due to gravity on a scale pan. We discuss the various experimental and theoretical aspects of this classic problem. Careful time-resolved force measurements allow us to determine the differences between the idealized problem and its implementation in the laboratory. We observe that, in spite of the upward force exerted by the pan on the...

QUICKSELECT Revisited

We give an overview of the running time analysis of the random divide-and-conquer algorithm FIND or QUICKSELECT. The results concern moments, distribution of FIND’s running time, the limiting distribution, a stochastic bound and the key: a stochastic fixed point equation.

Measurement on physical parameters of raindrop energy

Rainfall erosivity factor (R) is one of the most commonly used factors in soil erosion models. While rainfall energy (E) is the most elementary physical parameter to predict R. Based on comparative analysis of previous soil erosion models and rainfall erosivity factor measuring methods, integrated application of modern photogrammetric techniques, image analytic methods and automatic control the...

Falling Between the Cracks

The Falling Slinky

Consider a slinky that is held at one end while the rest of it is allowed to hang freely. If the slinky is released, then as it falls due to gravity it also shrinks in extent due to the contracting force in the slinky itself. A few years ago it was discovered that the net effect of these two changes exactly counteract each other at the bottom extent of the slinky and therefore the bottom of the...