Talk:Circular motion

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Please send me some example of gravitational motion! a test with answer! unsigned

What about vertical circular motion, such as an outside, noncentripetal force? This article never mentions it, a link (which I cannot find) or an explination would be nice. --1698 2006 01 08 01:40 (PST)

I do not understand what you mean, how can a motion be circular without centripetal force?--Patrick 12:23, 8 January 2006 (UTC)

Vertical, as in there is a centripetal force and circular motion, but there is also gravity that is not centripetal.--1698 2006 01 08 12:45 (PST)

Good point, I added the more general case including this.--Patrick 01:23, 9 January 2006 (UTC)

Thank you very much...I was doing some homework actually ;). --1698 2006 01 08 19:00 (PST)

The explanation of the word 'centripetal' appears in the article centripetal force. It should not appear in this article. Bo Jacoby 07:36, 27 February 2006 (UTC)

[edit] Jerk

I'm curious about the jerk vector of circular motion. I know it must exist, because the acceleration vector is a first degree vector. Deriving the acceleration vector yields the vector (x'''(t),y'''(t)), where x'''(t) = Rw3sinwt, y'''(t) = -Rw3coswt. I would imagine that if the instantaneous displacement would be described by the circle of motion, the instantaneous velocity by a line tangent to the circle of motion in the direction of rotation, the instantaneous acceleration by a line from the circle of motion towards the center of motion, that the instantaneous jerk would be described by a point at the center of motion. That’s only conjecture on my part, and I really don’t know enough about the subject to add it into the article, but it would be interesting to see the result of someone who does to do so.

[edit] Answer

The position is z=Re^iωt. Differentiation is d/dt=iω. Tripple differentiation is (d/dt)³=(iω)³ = −iω³. So instantaneous jerk is d³z/dt³=−iω³z=−iω³Re^iωt. The numerical value of the jerk is |d³z/dt³|=ω³R. The direction of the jerk is opposite that of the velocity. Bo Jacoby 13:32, 7 August 2006 (UTC)

[edit] edit on Dec.4

Seems as though someone had some fun.