conservation of energy

"Great spirits have always encountered violent opposition from mediocre minds." -Albert Einstein It may be hard to believe, seeing as how it's been our leading theory of gravity for nearly a century now, but Einstein's General Relativity is possibly the most frequently challenged scientific idea of all-time. Of course, it's emerged victorious from each and every one of those challenges, making a slew of unintuitive predictions that have been spectacularly confirmed each time they've been tested. Image credit: Miloslav Druckmuller (Brno U. of Tech.), Peter Aniol, and Vojtech Rusin. This…

So suppose you saw something that looked like this: This is a ball shot out of a shooter device. Well, it is a vypthon animation of a ball. What would you do if you came to see this video? If I had not made it, I would say it is an unrealistic video. It does not agree with my basic model of how things move after being thrown or shot or whatever. Interestingly (but unrelated) there was a set of physics questions that showed different possible paths of a thrown ball. The path representing the motion above was a common choice. Like I said, I made that animation. Here is another one. In…

Wow. In xkcd 681 comic, there is an impressive illustration of the common term "gravity well". Here is a small part of that large image: I can't resist. I must talk about this awesome illustration. My goal for this post is to help someone understand that comic (although the comic itself does a pretty good job). Energy Energy is the key here. Here, I will talk about two types of energy - kinetic energy and field energy. In this case, kinetic energy is basically just the energy associated with something moving. Field energy is the energy stored in the gravitational field. You could…

This was on my 'to do' list, but Tom at Swans on Tea beat me to it. Basically, this grocery store has these plates that when depressed produce electrical energy. Tom does a good job pointing out that this is not free energy (the original article says this also). Clearly, the energy comes from the cars. How much would this cost the cars? As always, let me start with some assumptions. The original article says that the bumps will generate 30 kW of energy every hour. That is an odd thing to say. I am going to interpret that as 30 kW of power for all hours (every hour). They couldn't have…