A Pedagogical Model of Static Friction

frictionWhile dry Coulombic friction is an elementary topic in any standard introductory course in mechanics, the critical distinction between the kinetic and static friction forces is something that is both hard to teach and to learn.
In this paper, I describe a geometric model of static friction that may help introductory students to both understand and apply the Coulomb static friction approximation….

The laws of planetary motion …

… derived from those of a harmonic oscillator

KEPLERP. A. Horvathy
Kepler’s laws are deduced from those valid for a harmonic oscillator, following the approach of Bohlin, Levi-Civita and Arnold

1 Introduction
Kepler’s laws of planetary motion state that
1. K-I: A planet moves on an ellipse, one of whose foci being occupied by the sun;
2. K-II: The vector drawn from the sun to the planet’s position sweeps equal areas in equal
3. K-III: The squares of the periods are as the cubes of the major axes of the ellipses.
These laws can be deduced from the inverse-square force law and Newton’s equations of
…

Humans could fly on Saturn’s moon Titan

P5_1 You can fly
flying on titan

H.Lerman, B.Irwin, P.Hicks

Many humans dream of flying like a bird. Although it is not possible on Earth, it is on Titan.
This paper explores the dimensions of a wingsuit allowing a human to easily take-off from the surface
of Titan.
It was calculated that the wing area would be approximately 4.7 m2 assuming an initial run up speed of 6m/s.
This value is larger than the average wingsuit wing area of 1.4 m2.
For this area the human will have to run at a speed of 11 m/s, which has only been reached by a small number of humans….
…

Leonard Susskind: The Theoretical Minimum

In this course, world renowned physicist, Leonard Susskind, dives into the fundamentals of classical mechanics and quantum physics. He discovers the link between the two branches of physics and ultimately shows how quantum mechanics grew out of the classical structure. In this lecture, he discusses some of the basic logic in quantum mechanics and then moves into some more mathematical concepts.

Read also: “The man who proved Stephen Hawking wrong