Intro Physics

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Category archives for Intro Physics

Quick, hit the brakes!

A reader emailed me a fun question from a physics exam he took, along these lines: A car driver going at some speed v suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid hitting the wall? My first thought…

A train leaves Cleveland…

The new academic year is starting, and if there’s one thing students love it’s a good word problem. If Sue is four times as old as John will be when Sue is one year than John… So in that spirit I was amused to find basically this kind of problem in a college physics textbook…

If you happen to be in the Bryan/College Station area tomorrow, you might consider checking out the Texas A&M Physics Festival. It’s sort of an open house with a ridiculous number of top-notch physics demonstrations as well as some very interesting talks. It’s free! I’ll be there helping out with some of the optics demos.…

Diavolo!

This guy is Allo Diavolo: He was a circus daredevil. At the dawn of the 20th century he worked on a number of stunts dressed in his ominous horned outfit. These days a lot of people, including me, have heard of him as an example in the pages of physics textbooks. In my case it…

The Amazing Spider-Man!

Spider-Man, of mass 90kg, is perching 10 meters above the ground when he notices his (depending on the continuity) crush/girlfriend/wife Mary Jane (50 kg) being menaced by… I dunno, a menace. I’m more of a DC fan really. He swings down toward her to spirit her our of harm’s way. Assuming he starts from rest…

Earthquake!

Every section of Physics 218 I’ve taught this semester has asked me about this question. Really it’s less of a physics question than it is a math question, but either way it gives people fits. It’s not all that surprising. While it seems like it should be simple, to most beginning students it’s not at…

And the Cow Jumped Over the Moon

Poking around on the internet looking for interesting problems to assign the students I’m about to have this semester, I came across this one: How much energy must a 450 kg cow expend in jumping over the moon? Fig. 1: Buzz Cowdrin? Now hints and solutions are available on the linked site, so what I’d…

Gas in a (very small) box.

Before the physics, I want to point out one of the most interesting ScienceBlogs posts I’ve seen in a long time: Not Exactly Rocket Science discussing the body-swapping illusion. You should read it. Now, here’s a quiz I gave my Physics 201 students. Easy as usual, but I’m a sucker for these order-of-magnitude problems where…

Mechanics of Heat

One of the last things we cover in Physics 201 is heat. You all know what heat is: the atoms in a substance jiggle around or fly around freely if the substance happens to be a gas. Like all moving massive objects, these atoms have a certain kinetic energy. Now the problem is that they’re…

Storing Energy

This week I’m teaching rotational motion to my students. Here’s an easy problem from their textbook, which comes from the idea of using a flywheel to store energy. I’m modifying it from problem 9.41 in Young and Geller: Suppose we want to built a flywheel in the shape of a solid cylinder or radius 1.00m…