Xeni Jardin at 6:36 pm Thu, Jan 24, 2013
(thanks, Meredith Yayanos!)
You mean centripetal force – there’s no such thing as centrifugal force ( http://xkcd.com/123/ )
Dang. You beat me to it!
It says literally in the comic you linked to “Simply construct Newton’s Law in a rotating system and you will see a centrifugal force term appear as plain as day.”
In many engineering and physics situations it is perfectly valid to use a centrifugal force to simplify the mathematics. Depending on your frame of reference it is just as “real” as centripetal force.
If you believe Einstein, there’s no such thing as gravity either.
There is a “centrifugal force” if name something that.
Everyone here is correct. Saying there is no such thing as centrifugal force is a bit overly pedantic and smart-assed. I will say it in my classroom, but as a physics teacher, it is my job to be pedantic and after I believe that they understand that centrifugal forces are better described as tangential forces I will admit and acknowledge the meaning and usefulness of the term ‘centrifugal’. Centrifugal forces are technically tangential forces which when unchecked (unbalanced) by a centripetal force result in what we see here. Centrifugal force, even while better described by other forces, does mean something and communicate the situation.
The best way to explain these two is what I was told way back when. We were in the gym for a high school assembly of some sort. I honestly don’t recall the whole situation, but I know it had to do with science. In any case, the presenter pointed out that we were, individually and collectively, exerting a force (gravity) by sitting in the bleachers. He then stated that the bleachers were exerting an opposite force upwards, which was why the whole pile didn’t collapse. Then (the important part) he said that if we didn’t believe that, we should simply sit there for a couple hours and then notice how sore our butt was. I think he made his point. The Hamster Wheel works only because the Centripetal force offsets the Centrifugal force. If it didn’t, the hamster would fly into orbit…or at least into the cage wall.
Unfortunately only half right. You do describe correctly the concept of normal force. Namely, that force which stops an object from, say, passing through another. The rotating disk exerts a normal force on the hamster.
Now, centripetal force is not really a type of force, but a generic term that describes whichever force being used to keep an object in rotational motion, the normal force in this case, but the nickname can also be applied to the gravitational force that keeps the moon orbiting the earth.
Then, rather than saying that this force compensates a second, centrifugal force, we observe the acceleration provide by the force. This is Newton’s second law. The hamsters pressed against the wheel are constantly changing their velocity, by changing their direction of motion. The rate of change of the velocity is the acceleration which in this case is a vector that points towards the center of the wheel.
The centripetal force, a role played here by the normal force, provides the required acceleration.
But in then end, I think I should refuse to let physics get in the way of enjoying a good anecdote or punch-drunk hamsters.
If Xeni had posted using the word centripetal I would have thought she was being a pedantic brat. Much like the person who corrected her.
Please. Kent linked to an amusing comic and only “corrected” her in the same ironic spirit. The problem here isn’t pedantry, it’s reflexive literalism. Along with puerile name-calling.
Except the whole point of the comic is that it isn’t correct to correct people’s usage of “centrifugal force”… It seems to have gone over the heads of many people, but it’s the villain that Randall is showing as being correct in the comic.
*harp glissando and wavy lines* The Gravitron… the State Fair… the chili dog… the horror…
Makes me wonder whether hamsters experience dizziness the same way humans do.
We could test for that, but we’d need a guinea pig.
My cat likes to sit on my office chair so one time I spun her really fast for a minute. She was so dizzy she fell over. It really surprised me. And made me feel bad. But I laughed anyway.
She *meant* to do that!!
As a physicist, my response to this video and the force debate is ” :3 ”
centrifugal? centripetal? whatever.
I just know that I want to be reborn as a crazy hamster! 8-D
I think we’re all missing the main point here: hamster barf is the cutest barf EVAR.
“Now where do you think you’re going? Oh, me tooooooooooo . . . . . . .!!!!!! “
“Centripetal force is an engineer’s phantom!” Aurther C. Clarke from Rama, it’s acceleration, not a force right? Isn’t that the real argument.
I like the part where they went around in circle.
I think the main scientific point of this video is that Hamsters Just Want To Have Fun!
See also http://www.youtube.com/watch?v=KDrpPqsXfVU
Things are squashed towards the outside in a centrifuge. If you say centrifugal force everyone will know what you are talking about.
Science schmience. I like how the one hamster is getting forces exerted all over its ass and the other one just keeps on going.
Everyone’s getting pedantic about the physics terminology, yet NOBODY has pointed out that those are clearly gerbils and not hamsters?
I’m going to need to see this recorded at 1000 fps to be able to truly figure out what’s going on.
I swear I heard a bunch of tiny little cries of “WHEEEEE!”
Meth: not even once.
Hamster running gleefully: Older brother. Hamster spun around relentlessly: Little sister. Trust me.
And those are mice, not hamsters!
Those are roborovski hamsters. I have one. Sleeps most of the day; runs six consecutive marathons (proportionate to his size) each night.
Thanks. They don’t look like the fat-cheeked fur-balls I knew.
Centripetal force is the force applied by the bowl to the hamster along the direction of the radius of the bowl towards the center. It’s the force that keeps the hamster moving in a circle instead of bursting through the bowl’s wall.
If you write down the equations of motion in the hamster’s reference frame, then the coordinate change introduces a term called “centrifugal force,” which accounts for why the hamster feels pressed against the wall like you do in a gravitron. Physicists often call that a “fictitious force,” but it’s only “fictitious” if you think the laboratory reference frame has some special “reality” status. It doesn’t.
Should not have watched this at school library.
… thus proving that hamster do not barf.
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