Re: Pendulum mechanics

Hal (
Sat, 19 Jul 1997 11:27:27 -0700

At 10:30 PM 7/18/97 -0400, Michael Lorrey wrote:
>But what is the energy put into? If true action/reaction holds, the
>rider moving its center of gravity higher will only reduce the momentum
>at that point in the swing, so it will not move any higher. If true
>action/reaction holds, as it is popularly understood, the rider should
>not be able to gain any momentum on each swing without causing a

I have a hunch that if you come to a thorough understanding of this phenomenon
you will understand why your "Lorrey Drive" will not work. I initiated a
thread on sci.physics last week about another momentum-conservation-violating
"space drive" which you had referred to a while back, and which is available
at the online IBM patent server. It would be helpful for you to attempt to
understand why that device will not work, either.

The point you are missing is the existence of Coriolis forces when a mass
moves in a rotating reference frame; and further, that a "pivot point" can
experience forces in other than the radial direction. In the case of the
swing, the pivot point where the swing is attached is itself pushed back and
forth, but being attached firmly to the Earth the motion is not noticeable.

Consider in particular the case where you are crouched in a swing, moving from
left to right, and you suddenly stand up as the swing goes through the vertical
position. By conservation of angular momentum, you can see that your horizontal
velocity will increase. But by conservation of linear momentum, some other
object must increase its velocity to the left to counter your increased
momentum to the right. That object is the Earth, and the pivot point will feel
a force to the left as you stand.