# Just an easy question-

1. Jan 8, 2005

### bomba923

Brachistochrone derivation

I have calculated the parametric equation for it....but why is this path a cycloid? It does seem fast...but how did they determine that it was a cycloid...not any other function?--Hmm-why exactly does the path of a point of a circle as it rolls down a straight line become the fastest distance between the two points in the brachistrone problem??

Last edited: Jan 8, 2005
2. Jan 8, 2005

### da_willem

Why is it a cycloid? Because it makes 'the best use' of the gravitational force. At first the path is very steep, so the object acquires a large acceleration, and because teher is no friction involved the object keeps this large velocity till the end of the track. Ofcourse there are other paths with the same characteristics, and I think it is a cycloid because this follows from the formulas.

If there is a connection between the shape being the one of a piont on a horizontally moving wheel, and the brachistochrone I would definitely want to hear more...!

3. Jan 8, 2005

### dextercioby

Mathematics and only mathematics.It could have been any other curve similar in shape,but it was the equations that led to the solution.

There's no connection between the cycloid followed from a point on rolling wheel and the brahistochrone.The point would describe the same cycliod even in the absence of gravity.

For more detail,check out this wonderful site:you have a model of brahistochrone right on the first page
site
It's in french...But it's math.It's comprehendable.

Daniel.

4. Jan 8, 2005

### bomba923

That's was my question in the first place--! Anyways, I'll try to figure it out

5. Jan 9, 2005

### dextercioby

Please,do tell us if u find it.It would be a really interesting both mathematically and physically result.

Daniel.