rallain | March 23, 2010I already looked at ESPN's Sport Science episode where they calculate that Marshawn Lynch produces 54,000 watts when pulling some tires. Yes, that is way too high. However, what would happen if some was actually that powerful? What could that person do? How fast could they run 100 meters? That is what I am going to calculate.
First, I am going to assume that Marshawn has a mass of about 100 kg. Also, let me say that he can produce 54,000 watts no matter what his speed.
Take a short time interval. During this time, Marshawn will increase his speed from say v1 to v2 this would be a…
rallain | March 23, 2010I happened to catch two parts of two different episodes of Meteorite Men - a show about two guys that look for meteorites. In both of the snippets I saw, they were talking about a debris field for a meteor that breaks up. In these fields, the larger chunks of the meteorite are further down in the field. Why is this?
Let me approach this first from a terminal velocity view. This requires a model for air resistance. I will use the following:
Where:
rho is the density of air
A is the cross sectional area of the object
C is a drag coefficient that depends on the shape of the object
v is…
rallain | March 22, 2010This is a topic that I am going to talk about in my physical science class. Might as well make a post about it, right?
Here is the deal. You are in a pool. You drop a quarter in the deep end and swim down to get it. I know the first thing you are going to ask: Why do I have a quarter in the pool? Does it matter. What matters is that your ears are killing you. Boy, that hurts. Why do your ears hurt and what can you do about it?
Pressure and depth
When you put a fluid in a gravitational field (like on Earth), the pressure in that fluid (or gas) increases as you go down. Why? There are…
rallain | March 19, 2010Let me be clear. I am not really an attacker. If someone wrote a report about ski jumping or something and misused the word "momentum", no big deal. However, if you have a show that claims to be about SCIENCE and you are obviously putting a lot of money into this show AND a whole bunch of people will see and think this is science - then you need to be a little careful. I think shows like ESPN's Sport Science are a good idea - you know, introduce some cool science ideas by using cool sports. This show just needs some help.
Yes, I know I make mistakes. I try to correct them when I become…
rallain | March 16, 2010Pre Reqs: vectors, forces
This is typically the first topic in the second semester of introductory physics - the interaction between objects with electric charge. There are 4 fundamental forces that physics typically looks at:
Gravity - an interaction between objects with mass - wow, I don't have a post on the universal law of gravity?
Electromagnetic - an interaction between objects with electric charge.
Weak Nuclear - an interaction between (let me just say for simplicity) leptons.
Strong Nuclear - an interaction between hadrons.
I know those last two are complicated - but I am not going…
rallain | March 16, 2010The other day I was having a discussion with my brother about software and free software. Somehow I said I like it when software is free. Since he is a programmer and likes to get paid to program, he said "education should be free." I think I might agree with him.
I previously talked about higher education, specifically how it was more about being human than about job training. With that in mind, shouldn't it be free? If everyone should get healthcare, I think everyone should get an education.
But wait! How would I get paid? I haven't really thought this through the whole way. But…
rallain | March 14, 2010Oh, I know you missed it. Really, it wasn't your fault. Pi day fell on a Sunday, so how are you supposed to have pi-day activities in class? Don't let it stop you. You are better than that. Do the activity anyway. What to do? Here are some suggestions. (Suggestions aimed mostly at the high school level)
Plot Diameter vs. Circumference
This is a great one. Let your students find as many round things as they can (cylinders work the best - or flat stuff). Measure the circumference (you can use a string or a tape measure) and the diameter. Since the relationship between these two is…
rallain | March 13, 2010Do you have an iPhone? I have an iPod Touch. Do you use vectors? Do you think RPN calculators are the bomb? Here is a RPN calculator for the iPhone that supports vector notation. VCalc by Silicon Prairie Ventures Inc. Oh - it is free. Here is a screen shot.
I played with it some, the only thing that would be cool would be a landscape mode.
rallain | March 13, 2010The most basic explanation of Pi is that it is the ratio of the circumference to the diameter for a circle. That seems simple enough, but it turns out that Pi is an irrational number - so you can't just write it down. Oh, I know that you are an uber-geek and you could recite the first 80 digits of Pi. But the question is - how many digits are enough?
In this post, I am going to assume that we don't know the true value of Pi (which is essentially true). I can then use propagation of error techniques to see how dependent different calculations are on the value of Pi.
Super Brief Intro to…
rallain | March 11, 2010I already went over a Monte Carlo method for estimating Pi - you know, for Pi-Day (March 14). Well, here is a small addition. This is the same thing done in Scratch.
If you create an account on Scratch, you can download the code of any project. I like Scratch.
rallain | March 10, 2010Pi day is March 14th - get it? (3.14) I am a big fan of Pi. Here is my first post to celebrate the awesomeness of Pi (I know this is early, but I was too excited to wait).
How can you determine Pi?
Oh sure, tons of high schools do the classic experiment. Measure the circumference and diameter of as many round things as possible. Plot diameter vs. circumference. The slope will be Pi. Really, this is a great lab to do for all sorts of ages. The key thing is that students can see what Pi really means. I am not going to talk about this lab, I am going to do some thing cooler.
What if I…
rallain | March 8, 2010I know many readers like the fermi questions (like how much would it cost to review all youtube submissions). Well, you are in luck - Diary of Numbers is having an estimation contest. Here is the question:
Mario has appeared in over 200 video games as Nintendo's main mascot. He has starred in TV shows, comic books, and feature films, but anyone who's played one of his games knows it's not all fun and games for the lovable plumber. He is constantly falling down bottomless pits, getting eaten by giant mutant mushrooms, and otherwise killing himself all while trying to save a princess who is…
rallain | March 8, 2010Hat tip to Frank for sending me a link to this video:
If you have never done a demo like this (without the motorcycle), you should. It really isn't too difficult. Here is a video of my version:
Inertial demo from Rhett Allain on Vimeo.
So, the question is: is the motorcycle thing real or fake?
First, let me talk about the key aspect of this demo. Why don't the glasses move? Well, they move - but just not very far. The demo is supposed to be an example of Newton's Second law, or you could say it is the momentum principle (which is what I will use). If a force is applied for a short time…
rallain | March 4, 2010Check out this thing.
That is where the guy (Jem Stansfield of BBC's Bang Goes the Theory) shows how he built this thing. Here is part 2 where he uses it to climb a building.
Here are some questions:
Why does it not matter how powerful the vacuum is?
How does a vacuum cleaner work anyway?
How does the vacuum cleaner work?
I know this is not HowStuffWorks.com, but I guess I should show some stuff. The cool thing about a vacuum cleaner (think shop vac so that I don't have to deal with the brushes) is that it is just one thing - a fan. The fan essentially moves air out of the vacuum part of…
rallain | March 2, 2010Perhaps an alternate title could be "hey, lets have class outside." I think I understand why students say this, but my standard answer is "no". Oh, but there is XYZ that we need to do. Here is the point I am trying to make - class is for students. Class is not for me. Students pay for classes, so they should get them.
Here is the other point. If a student chooses not to come to class, that is the student's choice. I am ok with that. Maybe it is not a great idea, but these are adults. There can be a problem. What if the class has attendance as a grade? What if the class will give a…
rallain | March 2, 2010Note: The following is a repost from some time ago. Today is the officially day to celebrate Dr. Seuss, so here is my Seuss-related post. Enjoy.
In the second Cat in the Hat book (I think it is the second one), the Cat reveals that he has more smaller cats under his hat. They are labeled A - Z with Z being so small you can't even see. Question: What is the sequence of sizes for successive cats? How big would Cat Z be?
Here is the first picture that Cat reveals Cat A. It is not trivial to measure their relative sizes because they are in different positions. I drew two circles, one…
rallain | March 1, 2010There was a Buzz Out Loud episode in the not-to-distant past where the discussion of youtube came up. I can't remember the exact details, but the main point was that it would be impossible for google (the owners of youtube) to review all of the videos that were submitted.
And here is my calculation. How much would it cost google a year to do this? First, I need to pick some variables (and I will first do this symbolically - then you can put in your own values if it makes you happy).
Submission Rate (s): This is how many minutes of video are submitted each minute (so the units would be…
rallain | February 28, 2010I ride my bike and mostly the wind makes me unhappy. On a very few days the wind is with me on the way to work and then changes so that it is with me again. But most days the wind is fairly constant. So, if the wind is constant then shouldn't everything even out? (Even Stephen).
Assumptions:
Let me start with the assumption that I (a mere mortal) can output at a constant power (but not 57,000 Watts like some people). I will also assume an air resistance force that is proportional to the square of the relative air speed. Here is a diagram.
A couple of quick things to point out. First,…
rallain | February 25, 2010I thought this was an interesting idea. One of my colleagues does not collect homework. Instead, the students turn in a sheet that lists which homework problems they worked on and how much time they spent on homework. By doing this, the students get a small homework grade - independent of how much time they claim they spent. I am pretty sure it is not a large percentage of the total grade.
Along with this "report", the students are supposed to keep notes on the homework they claim they did - just for reference. Theoretically, the instructor could verify that the student did the problems…
rallain | February 23, 2010I had so much fun creating graphs for the Red Bull Stratos Space Jump calculation, that I figured I should make some more.
Can you fall faster than terminal velocity? That is the question.
Air Resistance
Air resistance is a force exerted on an object as it moves through some stuff - air in this case. The magnitude is usually modeled as:
Rho is the density of the stuff the object is moving through
A is the cross sectional area of the object
C is the drag coefficient of the object - this depends on the shape (a cone would be different than a flat disk)
v is the magnitude of the velocity of…