## Wednesday, January 4, 2012

### Quick Physics Lesson

Well hey there!

Looks like I haven't done a blog post in a while. By that I mean in almost a year.

I was sitting around trying to write a paper, and instead I decided to write this post. It was something I'd though of a while ago, and I thought it was worth sharing.

Here goes:

In science, a derivative can be loosely defined as a rate of change of something due to something else changing.

For example, let's say you're driving in your car. It's pretty easy for you to check how far you've gone: you just look at your odometer. If you're less clever, maybe you count the trees you've passed. The possibilities here really are limitless.

We can call the distance you've gone your displacement. The derivative of your displacement, the amount of distance you've covered over a certain time (the rate of change of displacement due to time), is your speed. That's why your displacement could be measured in meters, but your speed is meters per second.

That's pretty easy. Let's say you weren't changing your distance uniformly (aka your speed was changing). Then you'd be accelerating or decelerating. The was to measure this is the change in speed as a function of time, or the change in the change in displacement due to time, due to time. This is the second derivative of displacement to time, and is measured in meters per second squared.

"What's the third derivative?" I can almost hear you shouting. Well, it's called a jerk. It's a measure of how variable your acceleration is. This can be explained by thinking of an elevator - as long as you're accelerating at a constant rate, you feel heavier or lighter, but as that acceleration changes you either feel increasingly heavy, or increasingly lighter (it's changing due to time).

After that? A change in jerk due to time is a jounce. It's how much your jerk changes from time, which means almost absolutely nothing in real life. Apparently it's useful for rollercoaster and fighter jet designers, where absolutely sudden unpredictable changes to speed, acceleration, and position happen all the time.

What's really great is what happens next. Some people apparently call the fourth, fifth, and sixth derivatives "snap, crackle, and pop", while the following derivatives are known as Lock, Drop, Shot, and Put.

And in case you were wondering, I have no idea what on earth one would need to measure those last few on.