The controvery continues!


The Bee published letters to the editor belabouring my understanding of physics. Poor Kyle’s been pulled into it too. Someone edited his caption and re-ran the picture with “centrifugal force” as the explanation. Who did this?

Centrifugal force pins riders

Re “State Fair’s thrills, chills are chaos theory in action” (Page A1, July 26): Oh my goodness. As one who studies physics as a hobby, I was stunned to see another example of how little is understood about, well, everything. The caption accompanying the photo on the back page states that the Starship 3000 ride “depends on friction: As it spins ever faster, riders are glued to the wall; when the wall rises, their feet leave the ground.” So that those (along with the caption-writer) who may have cut class that day in eighth grade don’t operate under false notions, let me make clear that what holds the thrill-seekers in place is not friction, but centrifugal force.

– D. Mark Wilson, West Sacramento

Improve science knowledge

The caption to the photograph that shows kids riding the Starship 3000 notes that the ride “depends on friction.” Anyone who took basic physics in high school should know that it is centrifugal force, not friction, that the ride depends on. I am starting to appreciate how scientific knowledge is becoming a rare phenomenon. Explains all the climate change denial.

– Stephen Lightner, Camino

I had a lengthy exchange w/ Mr Lightner, actually. I’m surprised to see his letter here.

Here’s the problem though. Now Kyle is being berated by physicists:

Some excerpts:

Two letters to the editor in today’s Bee claim that Starship 3000 riders are held against the wall by centrifugal force, not friction. Despite assertions to the contrary, the Bee had it right the first time. While centrifugal force is present, it’s acting horizontally, and isn’t what counters gravity’s vertical force. The force that’s stopping riders from falling is friction, and though this force is made greater by the increasing centrifugal force, it is the only one acting vertically (and therefore the one actually keeping the riders in place).


To the editor:

The letters and the picture caption (July 31, 2010) that claim that “centrifugal force” and not friction is responsible for riders of the Starship 3000 rotor ride remaining pinned to the wall are not correct. The only thing wrong about the original caption stating that the ride “depends on friction: As it spins ever faster, riders are glued to the wall; when the wall rises, their feet leave the ground” is that it is not the wall that rises but the floor that is lowered. If there were no friction, the riders would follow the floor, pulled down by gravity, which does not disappear when the rotor is spinning. Instead, as the velocity increases, the force of gravity is eventually matched by a force of static friction, preventing downward motion of the riders along the wall. There is no “centrifugal force”: A body tends to move in a straight line unless acted upon by an outside force, which is this case is supplied by the wall constantly pushing the riders toward the center of the rotor, causing them to move in a circular instead of straight path. As this force increases, so does the friction force perpendicular to it that opposes the force of gravity.

Richard Breedon
Research Physicist
Dept. of Physics, UC Davis

Now you’ve done it Bee! Couldn’t just trust me?


6 thoughts on “The controvery continues!

  1. Andrew says:

    Uhhh… actually the back sliders are at an reclined angle, so friction is not necessary. The normal force is slightly upwards.

  2. Lulu Liu says:

    oh yeah? what would you prefer to say

  3. Kim Tolley says:

    Will you stay on at the Bee? They could use your help!

  4. Lulu Liu says:

    Just freelance– I’m looking for a more full-time job

  5. Richard Breedon says:

    Hello Lulu,

    I saw your article in the APS News, and recognized the story about the reaction to your article about the fair ride in the Bee. I then did a search for your name and found that you posted my letter to the editor in your blog.

    I hardly believe it is fair to say that I “berated Kyle.” I had been visiting my family is SE Asia and did not see your original article, only the ignorant letters in response to it and Kyle’s “corrected” caption. In fact this is what Kyle wrote to me in response to the letter you post: “I greatly appreciate the show of support the the original assertion in the article and my caption. For some reason people seem to discount Lulu’s physics degree from MIT for their one high school physics class 30 years ago.” He does not sound so berated to me.

    Since I had not seen the original article, I did not know who Lulu was, but now I do.

  6. Lulu Liu says:

    No no no, Dr. Breedon, your reply was very professional and even-tempered, and believe me, I was glad to see it. “Berated” is of course tongue-in-cheek. Just finding a bit of humor in all of this. Hope you’ll forgive me 🙂

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