Posts tagged physics
Pressure and Surface Tension
- 29 January 2025
When it comes to fluids, there’s a few things that were never explained on my first introduction to the subject. In this post, I intend to explain why pressure is the same in all directions, and what surface tension actually is.
Consider an infinitisimal wedge in the \(xz\) plane, where the cross section is along the \(y\) direction.
Jumping off a Train
- 28 January 2025
Recently, I came across this cool problem (which is from Kleppner and Kolenkow, as well as INPhO 2014):
Two men, each with mass \(m\), stand on a railway flatcar of mass \(M\) initially at rest. They jump off one end of the flatcar with velocity \(u\) relative to the car. The car rolls in the opposite direction without friction. Find the final velocities of the flatcar if they jump off at the same time, and if they jump off one at a time. Generalize to the case of \(N ≫1\) men, with a total mass of \(m_\mathrm{tot}\).