williams@kirk.DEC (John Williams 223-3402) (04/04/85)
1) The track length is useless beyond a certain value. The water pressure will increase as you go down in depth, causing the displacement to equalize diagonally across opposite sides. 2) The position of the weights show that the vector addition of the gravity vectors for these weights will cancel out any force supplied by the displacement. John Williams
jr@bbnccv.UUCP (John Robinson) (04/09/85)
In article <1501@decwrl.UUCP> williams@kirk.DEC (John Williams 223-3402) writes: > 1) The track length is useless beyond a certain value. >The water pressure will increase as you go down in depth, causing >the displacement to equalize diagonally across opposite sides. Can't a wider track allow for many cups attached within the workable depth? If we can assume small enough friction in the chain/belt system, their small additional forces should help. Also, as long as each pair that is at the same depth contributes a non-zero net force, the chain as a whole is still helped. > 2) The position of the weights show that the vector >addition of the gravity vectors for these weights will cancel out >any force supplied by the displacement. I miss the point here. Are you trying to say that the displacement difference is countered by a torque resulting from movement of the center of mass nearer to/away from the center of the system? Like the original poster of this problem, I have never heard a satisfactory (to me) explanation of this PMM. I encountered it long ago in a high school physics class; in fact, I was just describing it to some of my coworkers in the hall, and then it appeared here! If my friends come up with the answer, I'll post it. /jr
js2j@mhuxt.UUCP (sonntag) (04/09/85)
> Like the original poster of this problem, I have never heard a > satisfactory (to me) explanation of this PMM. I encountered it long > ago in a high school physics class; in fact, I was just describing it > to some of my coworkers in the hall, and then it appeared here! If my > friends come up with the answer, I'll post it. > /jr Could someone repost or mail me a description of the membrane cup PMM? I seem to recall that it was about a chain of containers half-full of water with a rubber membrane stretched across the opening. The chain of cups was placed in the water so that on one side of the chain the cups were inverted. That's all I can remember of the explanation, but there must be more, because there's obviously no reason to expect the system I described above to move at all, let alone perpetually. -- Jeff Sonntag ihnp4!mhuxt!js2j "You're from Joisey? I'm from Joisey!" "Which exit?"