equilibrium

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What is Arnold made of?

Of course I am talking about Arnold Schwarzenegger. After looking at how many bullets he carries in Commando, I remembered this scene (also from Commando) (warning: maybe some not great language and some killing. You have been warned) If you don’t want to watch that clip, here is a shot (sorry for the quality). Clearly…

Oak Trees are awesome

In this part of the world, we have oak trees. Technically they are called live oaks – but I don’t get it. Of course they are alive. I was at a soccer game and this is the tree I always look at. Look how far those limbs extend horizontally. That branch is about 12 meters…

Pressure demo: suction

How does a suction cup work? It is all about the atmosphere. Here is a demo. Take some type of “suction cup” device. In this case, I used a toy dart. Stick it to something smooth and lift it up. Like this: What lifts up the metal block? The atmosphere. Diagram time: But this isn’t…

Yo-Yo: Rolling, sliding, pulling

This is actually been sitting around for a while waiting for me to post it. Here is another short Christmas-toy demo. I am going to pull this yo-yo at different angles and on two different surfaces. Check it out. What is going on here? Let me look at the first case where I pull the…

Friction Demo with a meterstick

This is one of my favorite demos. Easy to do and doesn’t really require any equipment. The basic idea is that you support a meter stick horizontally with two fingers. Slide your fingers in and they will both meet at the center of mass. Here is a video. Meterstick friction demo from Rhett Allain on…

Basics: Free Body Diagrams

**Pre Reqs:** [Intro to Forces](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php), [Vectors](http://scienceblogs.com/dotphysics/2008/09/basics-vectors-and-vector-addition.php) Hopefully now you have an idea of what a force is and what it isn’t. What do you do with them? The useful thing to do with forces is to determine the total force acting on an object. At the beginning of the introductory physics course, you will likely…