work-energy
rallain | November 4, 2008**Pre Reqs:** [Work-Energy](http://scienceblogs.com/dotphysics/2008/10/basics-work-energy.php)
You need to be familiar with work and energy to understand this. If you are not familiar, look at the pre requisite link. Ok? Now, let's begin.
Suppose a ball moves from point A (3 m, 3 m) to B (1 m, 1 m) at a constant speed as shown in the diagram below:
Suppose there is some other force (like my hand) also exerting a force on this ball to make it move along this path at a constant speed. What is the work…
rallain | October 20, 2008**Pre Reqs:** [What is a Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
[Previously, I talked about the momentum principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…). Very useful and very fundamental idea. The other big (and useful) idea in introductory physics is the work-energy theorem. Really, with work-energy and momentum principle, you will be like a Jedi with a lightsaber and The Force - extremely powerful.
Well, what is work? What is energy? How are they related? In [another post, I talked about energy.](http://…
rallain | October 4, 2008I think it is time for me to talk about energy. My ultimate goal is to give some insight into the many stories about perpetual motion. To do this, I will first talk about the fundamentals of energy.
**What is Energy**
I started thinking about this, and at first I realized that I did not have a good, short explanation of energy. The most commonly used definition in science text books is:
*Energy: the ability to do work (or something dreadfully vague like this).*
But what is work? It may be no surprise to find that many college level physics texts avoid defining energy. After some serious…
rallain | October 2, 2008I was recently re-watching a MythBusters episode and I found something I had wanted to explore previously (but accidentally deleted the episode). Here is a short clip from the "shooting fish in a barrel" episode:
Did you see what I found interesting? That big barrel of water left the floor from being hit by a bullet.
The question here is: Does a bullet have enough energy to increase the gravitational potential energy of the barrel to that height?
First, let me gather some data. From the episode, the Mythbusters were firing a 9mm pistol round into the barrel. I don't know much about…
rallain | September 30, 2008Which wastes more fuel? (and thus produces more carbon dioxide). This is a difficult to question to answer for a variety of reasons. The main reason is that a speed change from 71 mph to 70 mph is different than a reduction from 56 to 55 mph.
First, let me be clear that the question of how much fuel is wasted using daytime running lights (or DRL as they are called) has already been addressed. The first source I found was howstuffworks.com
**Assumptions**
The daytime running lights on a car run at about 100 watts (for the pair)
The energy density of gasoline is 1.21 x 108 Joules/gallon.
A car…
rallain | September 14, 2008Can you believe it? Have you seen this video?
Are you thinking what I am thinking? WOW. How could these people not follow my rules for cool internet video. Once again, here they are:
1Keep the camera stationary. This way I don't have to keep moving the origin in the movie.
2Don't Zoom. Same reason, this video followed that rule.
3Include a clear and obvious calibration object. A meter stick would work, or even a Kobe Bryant (I can look up his height). Maybe it could be a Ford F-150 that has a known length. Something!
4Include the mass and height of all people involved.
5Use high…
rallain | September 14, 2008Friction in Line Rider
Is there friction in Line Rider? Does it function as physics would expect? To test this, I set up a simple track:
Basically, a slope with a flat part to start with and to end with. Let me show you something simple before further analysis:
This is the x-position vs. time for the line rider on the first horizontal portion of the track (before he or she goes down the incline). This shows the rider…