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A. wins 365-267

How powerful is a physics professor, anyway?

Over at Dot Physics, Rhett has been explaining the inaccurate calculation of power on a TV show that I have never heard of or had the chance to see. He posted a video of himself pulling the family minivan with the family inside. He even posted a video of his 6-year old pulling the vehicle!

I assume that in a future post, he'll be giving the right way to calculate the power, but I couldn't resist trying out video analysis in Logger Pro with his video.

I analyzed the first 3.5 seconds after the van starts to move by clicking on the same point on the van every few frames. I used the wheel base of the 2007 Mazda 5 as a guess for the scale calibration.

I was pretty surprised that on my first attempt, the position-time data had a nice parabolic shape. I could have probably spent a little more time making sure that I always clicked on the exact same spot on the van, but for quick and dirty analysis, I'm pretty happy. Logger Pro defaults to motion to the left as having negative velocity. I didn't really try to reset this, as I only care about the magnitude of the rate of velocity change (i.e. the acceleration).

The acceleration is the slope of the velocity-time graph, so let's look at that:

Okay, so Rhett either wasn't applying a constant force over the 3.5 seconds, or my measurement uncertainties are starting to show up. Either way, the average acceleration can be estimated by looking at the slope of the best fit line. Logger Pro says that the average acceleration was 0.15 m/s².

So, using Rhett's free body diagram, we can apply Newton's second law:

The friction force in this case is rolling friction, so we need a coefficient of rolling resistance. The friction force is equal to the coefficient of rolling resistance times the normal force. The normal force (on the level ground) is just the mass of the vehicle multiplied by the acceleration due to gravity.

Rearrange to solve for the applied force:


I googled around a bit and found that a typical auto on concrete has a coefficient of rolling resistance between 0.010 and 0.015, so I ballparked it at 0.012. Rhett gave the mass of the car in pounds, so I converted to kilograms.

Finally:


I didn't carry out the video analysis the whole way through the entire movie. The van moves for about 9 seconds, and I know its acceleration was not constant, since the brakes were applied at the end. However, I'm sure that our physics professor could sustain the constant 300 N applied force if he wanted to all the way through the 5 yards (strange units they use in LA; we'll call it 4.57 meters). At the constant acceleration we measured, it should take him 7.8 seconds to pull the van that far.

So the work done by our professor is equal to the force applied (300 N) multiplied by the distance through which the force acted (4.57 m). His power output during the pull is the work done divided by the time:

300 N * 4.57 m / 7.8 s = 176 W

That's a mighty bright light bulb, but it's just under twice the power radiated (on average) by a human that is just standing around doing nothing.

I know he was pulling at an angle, so his applied force is larger by the cosine of the angle, which I guesstimated to by 15 degrees, so make the applied force 310 N and the power 182 W if you want to be nitpicky about it...

Two in a series of past travel exploits.

This is another blast from our past travels that I'm posting photos now only because of the Metafilter postcard exchange.

Sometime in 2005, my good friend from grad school invited (or I otherwise wrangled an invitation from him) Renae and me to come to his family's cabin in the French Alps for New Year's Eve that year. We planned an entire Paris/London/Alps trip around his invitation.

We flew from Chicago to Paris, spent about 2 days there, then took a train to the southern French Alps. Our friend picked us up and drove us to his family's cabin up in the mountains! Our first stop was at a small hut where everyone in his family was gathered to bake bread in a wood-fired oven. It was incredible!

The New Year's Eve celebration was outstanding! There was a multi-course meal, with oysters, foie gras, and many other delicious dishes. We started eating at 8:00 pm, and didn't stop until the champagne flowed at midnight. It was so, so, so cool!!!

Everyone in the family was so incredible hospitable and kind to us. We spoke not a lick of French, and they went out of their way to make us feel welcome. It truly was the best part of the trip.

I think we were planning to leave on the 3rd, but because of the holiday and because we had not booked a return train ticket to Paris, we had to leave on the 2nd. It was our fault for not booking a ticket, but we were used to traveling in 1996 on trains where you could always ride on trains as standing-passengers. I guess times had changed. So we stayed overnight at a hotel in Grenoble, then went back to Paris to catch the Eurostar to London.

Somewhere in Paris, Renae got sick (actually, hadn't been 100% well in the Alps) and probably got a bit of food poisoning from a weird fish pizza that she ordered at a cafe. She hadn't slept the night before we were supposed to catch the first train out in the morning, so we were bracing for a crummy ride from Paris to London.

We had bought our Eurostar tickets online a few months ahead of time. When I ordered the tickets, I bought coach seats ($65 each, I think) for the return from London to Paris. But the Paris to London trip, all the coach seats were sold out. All the First Class tickets were around $500 or more, which was way more than I wanted to pay. After poking around on their website, I had found some middle class ticket that was something like "Business Economy" or something similar. From all I could tell, it was going to be a coach seat for $30 extra. Having no other options, though, we bought them.

When we finally got to the train platform and were directed to our seats, it turned out we were in First Class. In fact, the Eurostar only has First Class and coach. An in our car, there was only a family of four sharing the entire car with us. The seats were comfortable; there was a real table for us to use; and the breakfast was simple, but refreshing. We got toast with jam, which was the perfect meal for Renae's stomach.

London was great, but knowing that we'd have to cram a lot into a little bit of time, we chose to do only highlights. We spent a lot of time running around to some of the major sites. We paid for an all-city bus tour that allowed us to hop onto and off of any bus run by a popular bus tour company. We saw the Mousetrap. We shopped at Herrod's. We wandered through one of the residences of one of the Royals. We did not hang around for the changing of the guard.

After a few days in London, it was the Eurostar back to Paris. Coach was like riding in a plane on Southwest Airlines. It wasn't too cramped, but we weren't exactly comfortable. And no one brought us toast.

We had another night in Paris, then flew home.

Somewhere in this post, I should have pointed out that right about the time the plane took off from Chicago to Paris, I looked at Renae and realized that having been married for five and half years, it was the first actual vacation travel we had taken that did not involve a physics conference in any way.

One in a series of past travel exploits.

			July 15 to 19 New York City

As part of the Metafilter postcard exchange, I decided to send out a bunch of old postcards that I have collected from past travels, but never got the chance to send out.

I wanted to do something extra as a part of the exchange, so I thought I'd post some photos from my trips and include the links on the postcards.

This trip to New York City was in the Summer of 2008. This was the last year for old Yankee Stadium and for Shea Stadium. Sometime during the early Spring or late Winter of that year it was announced that Billy Joel would play a concert at Shea. The concert was billed as "The Last Play at Shea". I'm a huge Billy Joel fan, and had seen him in concert several times before 2008. But, my wife had never seen him in concert, so I asked if she wanted to go. She said she would only go if my brother would go with us. We called him and he said he was totally in. That Saturday, we called for tickets and I was able to get through before they were all sold out.

When we got to NYC we were supposed to meet my brother somewhere in midtown. It turned out that the spot we were supposed to meet at took us right to the Major League Baseball All-Star parade. The photo above is of Ryan Dempster, who was in the game that year. The All-Star game was playing that year at Yankee Stadium.

We did lots of things on that trip, including walking from Central Park to Battery Park. We took pictures of our panda in various spots, including on the Staten Island ferry and in the terminal.

One of the places we wanted to go was to a place called Peanut Butter and Co. They sell unique peanut butter, which my wife had given to me one year for our anniversary. But they also have a restaurant that you can go to and get different gourmet peanut butter sandwiches. At the restaurant, I picked up some postcards, and these are some that I am sending out to the Mefites.

(The link below the photo will take you to a small gallery of photos from this trip.)

Since my last update on the 2-for-1 project in my room I have made some more progress. I've been able to clear off the table that does not have the computer on it. It was nice to be able to do a little grading on the table. I set up my roll of butcher paper on the top of the table and have been using that to take notes on as I'm working at the table.

Here's the latest stuff to leave the room:

• A handful of tools went to the garage

• 2 collector mugs (still in their boxes) went to the basement and will probably go out of the house this summer.
  

• 2 boxes of random projects and parts went to the basement where I'm putting all my current and future projects until I have time to work on them.

• A craft kit that I haven't had a chance to try out yet went to the basement.

• 2 stacks of papers/magazines/journals were properly filed, a lot of which went out with the weekly trash.

• My shop light for that I use for photography is going to live in the garage even though all my other photography gear lives in my room.

• 3 comic books that I discovered I had duplicates of were sent to a friend.

• Another paperbackswap book (a biography of William Randolph Hearst) was mailed out a week ago.
  

Also, an update to a few of the other things that I posted about previously: my firewire adapter that I put up for sale on ebay was sold but the data cable for an old phone did not sell on craigslist. I'll try relisting it either on ebay or craigslist again and if it doesn't sell, it will go to Goodwill.

Things that have come into the room:

• Stack of Christmas presents including a farkel game, a small poster, a toy robot and a CD. These have mostly been put away.
  
• A book I bought at a used bookstore.
• A power strip
• An Ikea tin for storing little things that tend to collect on the desk in the room.

Total items out for the year:

38

Total items in for the year:

13

Apple didn't like my homage to Nate Dogg

This is a screenshot of the podcast customer review page in the iTunes Store for one of the podcasts I listen to regularly. If you go read the reviews in iTunes right now, you won't see my review. It was removed, probably by Apple, most likely because of the critical comment I made about how someone at Apple did not like my full review of the podcast that I had tried to post before the one in the screenshot was posted.

When you write a podcast review on iTunes, you are presented with five "Tips for writing a great review":

• Keep them short and to the point. Average iTunes customer reviews are about 200 words.

  Mine clocks in at 238 words. Granted, it is formatted a little differently and looks longer, but it's no significantly longer than what Apple calls average.
  

• Praise podcasts on their own terms, not at the expense of other podcasts or the audience of other podcasts or genres.

  My review is nothing but praise, and says nothing about other podcasts or audiences of other podcasts.
  

• Take the time to copy edit your work so that you avoid embarrassing typos or grammatical errors.

  Good advice. Done.
  

• Do not use profanity or overtly sexual language.

  No problem here!
  

• Do not use language that can be construed as hateful, especially in regards to lifestyle, religion, or race.

  Nothing in my review has anything to do with religion or race, so that's a non-issue. With respect to lifestyle, I suppose you could make a case about the numerous references to drunks, but if you know anything about the podcast I'm reviewing, you know that the topic of alcohol and drunks comes up frequently in the podcast itself. In fact, it is often in the titles and descriptions of the podcasts as posted to iTunes. And, my review is not "hateful" with regard to any lifestyle, so I don't really see it as going against this tip, either.
  
  At the very bottom after you write your review (not to exceed 6000 characters, mine clocks in at 1200 characters) there is one more line:
  
  

  If a review is deemed inappropriate, it will not be posted to the iTunes Store.

  
  
  I did some searching online to see if there were other people who had their reviews rejected from the iTunes Store. The only relevant information I could find came from a FAQ for Podcast Makers on Apple's site:
  
  

  Can I have a review removed?

  iTunes does not remove reviews for editorial purposes. Reviews with profanity, hate speech, explicit/pornographic content, or commentary that is completely off topic are prohibited. To request removal of a review, click on Report a Concern for that review.

  Again, if you know anything about the podcast I was reviewing, you would know that every line in my review was completely ON topic for their show.
  
  My guess is that Apple doesn't want their Customer Reviews to become like the ones you see on Amazon. (e.g. The Story about Ping, Tuscan Whole Milk) Which is a shame. Because if fans of podcasts (or any content on iTunes) can't have fun to promote their favorite artists, everyone sort of loses an opportunity to discover something new.
  
  Anyway, the full podcast review that I wanted to post is here. My apologies to Warren G and Nate Dogg...
  
  [Andy:]
  Podcasters
  we podcast any speaking of his mind
  and we download em
  But you can't be any geek off the street,
  gotta be out of your parents basement, if you know what I mean, earn your keep!
  PODCASTERRS!!! MOUNT UP!
  
  [Broham:]
  It was a clear black night, a clear white moon
  Nick D was in the seat, trying to consume
  some talk in the eve, chattin' with a drunk
  I'm rollin in my ride, beers are in the trunk
  
  [Andy:]
  Just hit the Northside on the Kennedy
  on a mission tryin' to find Mr. Nicky D.
  Got a 'dog with fries and I need to chew
  all you drunks know what's up with 312
  
  So I hooks a left on Addison and Clark
  The Cubs are out of town so I said "Let's park."
  I jumped out the ride, and started to cough
  Nick went on a rant and my pants fell off!
  
  [Nick D:]
  Since Andy's tweetin' me I'ma check my phone
  Laughin' so hard that I start to moan
  Won'tcha load up your ipod with The Nick D Show
  You can do it right now or at your leisure, bro!
  
  [Andy:]
  He's speaking
  about a previous era
  Nick fans,
  Brew and view,
  I dare ya.
  Drunks
  Are in the News
  
  [Nick D:]
  Wisconsin's where they're from and the "winner"'s gonna lose
  
  
  Movies
  Music
  We brings
  Culture
  D-Funk
  where Chicago is home
  and home is Chicago