# Spinning an object in a perfectly horizontal circle?

### You are correct

A with so many things in Physics text books we make some assumptions. In the problems you do with your students we assume that when we say perfect "horizontal circle" that there is no real force of gravity. What we should really be thinking about is a pendulum moving in a circle. The force of gravity will be equal to the vertical component of the tension and the horizontal component will be the centripital motion. You can do this if you have done 2-d mechanics.

I would be curious for your students to do a percent error calculation and see how close it comes to the actual error in not factoring gravity/vertical tension

### Yeah... I was thinking of the

Yeah... I was thinking of the same thing - the % error would be interesting to see. Yes, and since we did 2-D dynamics, my students are totally capable of doing the true calculations. Thanks for answering (and agreeing with me), I didn't want to think I'm the only one thinking like this.

### Figured it out

I think it is theoretically and practically impossible to even pull a string with no extra weight tightly enough to be horizontal. The raising comes from pulling outwards (horizontall opposition), but in a perfect horizontal system there will be no upward vertical force from the pull.

As the string gets closer to horizontal, the flattening angle means there is less and less force pulling up and more and more, proportionally, pulling out. The force pulling up will approach zero. The closer you want to go to horizontal, the more total force you need to counter gravity. You will break whatever string you are using before you can get to horizontal as long as there is gravity.

### Yeah, that totally makes

Yeah, that totally makes sense. I think Mythbusters did an episode about something similar to this... Thanks for the comment.

### There is a post in a physics

There is a post in a physics forum that touches on this issue... here is the link if you're interested: http://www.physicsforums.com/showthread.php?s=a18660a8abd41b0089546ec091...

### You are the teacher. You tell

You are the teacher. You tell us. Well I was never good at physics but you kind of made me think on this one. Will post if I find any satisfactory answer.
Theodor from vista college

### I appreciate your theory of

I appreciate your theory of forces. But I just have read in the reference books that any object when comes in circular motion, gets stability when centripetal force is equal to forces on vertical and horizontal components.truck driver jobs

### This is a good,common sense

This is a good,common sense article.Very helpful to one who is just finding the resouces about this part.It will certainly help educate me.Swiss watches\\Rolex Watch