Category Archives: general physics

Does the hoop hop?

Posted on February 28, 2023 by Andy Rundquist

I greatly enjoyed this recent video from StandUpMaths: The set up is a hoop with a mass attached at one point. It’s rough so it rolls without slipping. It’s released with some angular momentum with the extra mass starting at … Continue reading →

Posted in general physics, math, mathematica, physics | 1 Comment

Planetary tunnel oscillators

Posted on February 26, 2023 by Andy Rundquist

Pick a point on the earth and start digging. It doesn’t have to be straight down. Keep it straight (careful! it’s harder than you might think) and keep going until you come back to the surface. Ok, now drop a … Continue reading →

Posted in general physics, mathematica, physics, teaching | 2 Comments

Dropping ladders

Posted on February 25, 2023 by Andy Rundquist

My friend Rhett Allain has really got me interested in this ladder drop posted by Veritasium: Here’s Rhett’s awesome explanation: Of course I wanted to see if I could model it with Mathematica, and, after finding I could run Mathematica … Continue reading →

Posted in general physics, mathematica, physics, teaching | 2 Comments

Rolling without slipping on curved surfaces

Posted on December 31, 2022 by Andy Rundquist

I’ve been trying to see if I can model balls rolling on curved surfaces and I think I’ve cracked it. Here’s a teaser to get you interested: What you see is a sphere rolling on a curved surface. The blue … Continue reading →

Posted in fun, general physics, mathematica, physics | Leave a comment

Shooting circuits

Posted on June 27, 2019 by Andy Rundquist

I’ve posted before about how I struggle teaching complex circuits (really just circuits that contain batteries and resistors in ways that can’t be analyzed with parallel and series tricks). There you’ll read about how I find that if I just … Continue reading →

Posted in general physics, physics | 8 Comments

Doppler Drum Corps

Posted on April 7, 2019 by Andy Rundquist

One of my favorite oral exam questions to give students in introductory physics classes is to ask them whether marching bands should worry about tuning because of the Doppler Effect (lots of details below but the short version: if there’s … Continue reading →

Posted in fun, general physics, mathematica, parenting, physics | 6 Comments

Mass changing orbits

Posted on December 28, 2017 by Andy Rundquist

A few weeks ago my good friend John Burk posted some intriguing questions about what happens to planetary orbits as the sun loses mass (all that heat has to come from somewhere!). I’ve been thinking about it ever since and … Continue reading →

Posted in general physics, mathematica, physics | 2 Comments

Faraday’s law is overused

Posted on November 2, 2015 by Andy Rundquist

First let me say that I thought for sure I’d written this post last year, but it appears not. That could also mean that maybe I didn’t write it because someone else had a good breakdown of my argument, but … Continue reading →

Posted in electromagnetism, general physics, physics | 6 Comments