Wednesday, October 11, 2006

Circular Motion - Episode 16

What do merry-go-rounds have to do with artificial gravity? Lean about the science of spinning when Dr. Carlson talks about circular motion and the centripetal force.

Science Theater Episode 16: Circular Motion


meaghersclasses said...

Great work Matt, a very creative use of podcasting in education. I've been experimenting with podcasts this year too, but without your panache, still receiving good feedback from students.
Richard Meagher.

Michael C. said...

From Caltech to teaching at Bigelow to torching your dignity over the internet, rather an interesting resume.

Anyway, just wanted to say hi and nice videos btw although the intro could use some special effects :.-)

-Your former 7th grade student

Dr. Matt J. Carlson said...

Hey Michael! Nice to hear from you. Unfortunately my SFX budget is a bit nil at the moment.. (unless you count transitions, I have LOTS of transitions...)

sillyshoelover said...

To go in a circle, you have to be pulled towards the middle of the circle. Also called centripetal force. Merry-go-rounds have to do with artificial gravity because when it goes in a circle, its being pulled in the middle but you feel like you are being pushed off the side. The platform from where the rides are placed on are being pulled down from gravity. The platform is what's being pulled towards the middle.

markholden said...

Very much liked your candle demonstration - i'd never seen it before. So i'll forgive you for forgetting Newton's first law in the excitement demonstrating the paper saw.
The paper doesn't want to fly out in all directions - the paper wants to keep moving in a straight line (as you would see if a piece was disloged. The only reason it doesn't is because it's connected to the rest of the paper disc.
Other than that keep up the good work

Dr. Matt J. Carlson said...

Thanks for the comments, Mark!

Everything you say is correct and to be clearer I should have addressed the issue of the rigidity of the paper in another way.

However, I would like to reserve the right to point out I didn't say anything incorrect either. As the paper is a disc, at any one point there is a part of the paper that would fly out (in a straight line) in any given direction. The paper doesn't want to move in a straight line, each part of the paper wants to move in it's own straight line. Technically, since there is a part of the disc willing to fly in any given direction at any given moment, the "paper" itself is attempting to fly in all directions. (Just tangent to the circle, not directly out from the paper.) This is easily seen if the paper were to shatter, shards of paper would fly in many directions, not all in one direction.

One reason I like relating to the "all directions" comment is that it makes it easier for people to understand it is the tension of the paper causing it to be an effective cutter.

markholden said...

With respect, Dr. Coulson, having watched the video again you use the word 'out' to describe what the paper is 'trying to do'. To the overwhelming majority of people would that not imply motion away from the centre of the circle? (That's the implication I took). Therefore I think that what you said is incorrect because it moves towards the dangerous territory of centrifugal force and only confuses and not clarifies a difficult Physics concept and one I have spent my working life trying to get across to students.

Dr. Matt J. Carlson said...


Centrifugal force is a concept that is often misuderstood (and does not apply here either). My comments could easily be misunderstood.

I'd still wager my comments are correct only "technically correct", but are clearly "misleading in spirit".

My attempt to avoid confusing the overall issue by getting into an explanation of centrifical (vs the non-existant centrifugal) force served to only reinforce the common misconception.