Quote:

Originally Posted by

**Jamt**
I don't see how you can first say that the height has increased with delta and then in the next sentence say that you cannot get any height amplifications.

A better approach to get amplification with a flat bottom would be to double pump. It is not possible without it.

It is gravity that enables pumping and it can be utilized in many ways. Without gravity you would have true conservation (would also need a full pipe)

Another way to look at things is the forces involved. The vertical forces pushing on the rider will determine how high he gets. It should be intuitively obvious that the forces are larger in the case when you extend at the bottom and flex towards the top than if you don't.

I have tried to explain in various ways how it works and I have even calculated an example. The next step would be to build this into a physics simulator, but that just feel like too much work at the moment.

Be my guest to prove that it is not possible. To prove that you need to show that the energy returned by flexing the legs close to the top is exactly equal to mg(delta h)

This is the end. This is my last post about physics. Don’t miss it. I’m sure many of you will give a sigh of relief. JanT, I hear that you have a Ph.D. in physics. We’re going to have to get our Ph.D. committees together for a conference, because one of our Ph.D.s should be revoked over this.

If you put energy E into a system and you get out kE, that energy is amplified by a factor of k. In a passive system, E in, must equal, E out, to satisfy conservation of energy. For a mass in a gravitational field, height is energy. If you put in a (delta)h into a passive system you have to get out (delta)h. If you get out k(delta)h, you’ve amplified, so you must have additional energy injected somewhere into the system.

In the halfpipe example, when you push against gravity you inject mg(delta)h energy. Your starting energy is mgh so your output energy must be mgh+mg(delta)h. For a spatially constant conservative gravitational field, it doesn’t matter where you inject that energy. You can do it at the beginning of the half pipe, at the end of the half pipe, on the flat spot in the middle or anywhere on the flat spot in the middle. When you move a mass against gravity you inject mg(delta)h energy.

This is by no means a proof, but I googled for 5 seconds and came up with a video below that shows how people approach these problems. This is how I was taught in my physics classes to approach these problems. This is how I approach these problems every day to produce innovative devices that tally and convert energy that I sell all over the world.

This concept is so core, that if I’m wrong my whole life is a lie and everything I’ve said is nonsense. I’m just another clamoring voice of nonsense added to the mix. What use am I? It’s futile for me to contribute. Or, I can’t even convince a Ph.D. in physics (with agreeing voices no less) the most basic physics 101 concept. What’s the point of being a voice of reason unheard and useless amid unreasonable doubts? Right or wrong, this shows my uselessness, and I will go back to finding ways to contribute that are more productive. This wouldn’t be the first time I’ve had to straighten out a Ph.D. in physics and it won’t be the last, but we need to be in person. This forum is not the place.

Edited by The Engineer - 5/7/15 at 7:37am