Recent content by Cri85

it don't turn in the lab frame reference A'D = 1.57R, but what is that distance ?

Relative to the support. For resume, I would like to know if the spiral push or pull the stem. I need to know the distance D1 to reach the spiral, because the spiral increase more and more and I need to know what the distance D2 the stem move because the stem is on the support and the stem is...

The disk rotates counterclockwise at 1.57R each quarter, like I drawn so the distance traveled is greater than the spiral ? The spiral push the stem ? Now, it depends of the distance AB ? If I take AB=1.57R, the spiral don't increase its "length" ?

Sorry if I don't understand. Like that ? http://imageshack.com/a/img913/8661/42rQHN.png B'D = AB -1.57 R ? It's the additionnal "length" (the spiral is far away) of the spiral after 90° ?

I try to do what you asked, I'm not sure to understand all your message, I drawn an image: http://imageshack.com/a/img661/4720/81Snwo.png I noted A', B', C', points after unwinding the string. It's correct ? But I don't understand why the distance is not the same.

Thanks ! I calculated some examples with the disk in the center of the support, and the distance is always 1.57R for 90°, like the disks turns counterclockwise, the stem moves of pi/2*R=1.57R, so the stem moves like the spiral, the spiral don't push nor pull the stem ? It is the same result if...

I guessed it was a Archimedean spiral, the exercice don't speak about the Archimedean but the image shows the perpendicularity in 2 positions, so it must be perpendicular always. I think it's possible to have a shape always perpendicular to the stem, in this case is it a Theodorus of Cyrene's...

True, I don't understood that point, I corrected my last calculation, like I see the picture R is choose for have the stem perpendiculary to the spiral, always. So, the equation of my spiral is ##x=−1.4\theta cos\theta## and ##y=1.4\theta sin\theta##. I have some trouble for find a general...

Homework Statement A red Archimedean spiral is fixed to the ground. An external motor turns a grey support clockwise at w, the support can only turn around itself. On the support there is one orange disk that doesn't turn around itself at start. A stem is on the support. That stem: - turns...

Homework Statement Does that container full of water gives a torque on Earth ? http://imageshack.com/a/img537/6733/9Y0Hqq.png Homework Equations -- The Attempt at a Solution I drawn all interesting forces : http://imageshack.com/a/img540/9315/ymwwvW.png Like that there is a torque...

I understood ! if I take a lot of small parts, it's logical, thanks. I thought the force was the same for an altitude for one container with air or not. But it's not the same weight. So I can reply to my another question: if the weight is the same with a fixed bubble inside ?: the answer is no...

Someone could explain to me why the force F is apply in the center of mass and not at the wall ? Why the work at step 4 is not the same than in the step 2 ?

Weigth*h/2 but I'm not sure, with h the height of the container

It depends how boxes are arranged. When the box move up or move down (in my cycle), nothing moves inside the container.

The same.