## 942 Reputation

11 years, 354 days

## @Rouben Rostamian  I found the refe...

@Rouben Rostamian  I found the reference in the for the proof of  1:2:3 inertia ratios

Yes, it is quite hard to find things in it.

## Importances.....

@Rouben Rostamian   Great solution and demonstration. From what I remember just assign the values of inertia. The simplest is 1:2:3 and that is the best inertia ratio set, for the effect. The body is just a graphic to demonstrate the effect. You would have to troll through the blog I referenced for details. There are other subtle effects based on the ratio of angular momentum and kinetic energy. If < 1 tumbles in one direction. If =1 tumbles only once. If > 1 tumbles in the other direction.

Is there a way to set the time increment in your solution because as the rotational speed is increased the body it appears to turn in the opposite direction? I was trying to see if the numerical solution would reflect the property of change in tumbling direction.

## A Blog on the Subject matter....

I followed this blog http://arkadiusz-jadczyk.eu/blog/2017/01/04/  on the topic last year from January to about April. Its is based on MMA and the physicist developes an explicit set of solutions.  I got it to work in Maple, with a good bit of help from Ark too, but it was a lot of work.Can dig out some of the simulations if needed.

Edit:- I have a Maple numerical solution aswell I found on line while looking for data last year. I can post that document later.

## Thoroughly explained....

@tomleslie This is a very detailed answer.  Good to know about [ ]. Solve can be a real pain at times with that.

I don't have a programming background and am self-taught (with a lot of help from here) on Maple. That is why I use the 2D input. I see one's eye would get tuned to your style. It definitely makes the code readable.

## What would you suggest?...

@Carl Love Ok. Good advice, that could cause some real problems. I guessed what I was trying wouldn't be recommended. What would you do to store a series of values etc, generated in a loop? I am also a using the equations Pedal||i later.

## Excellent. And a question or two....

@tomleslie  Thank you that works very well.
At several places, you have these brackets [ ]. What do they do?  How do you achieve the formatting of your code?

.

## Remove that line....

@Ramakrishnan   Sorry. I meant to remove that line. There is a procedure at the start called Trunc. It is normally stored in my package called RonanRoutines. I copied and pasted it into the doc so it should work for you. Am at work so will check tonight.

## # that line out...

@Christian Wolinski  Sorry. I meant to remove that line. There is a procedure at the start called Trunc. It is normally stored in my package called RonanRoutines. I copied and pasted it into the doc so it should work for you.

## Thank you....

@Christian Wolinski Thank you. Very workable. I would love to give you best answer, thumbs up. They are not available.

## Nice....

@Joe Riel That is nice proc and a big step towards the end goal. At this point, I am going to start a new question on reducing the equations as this one was primarily about plotting.

## A common problem....

@Joe Riel Thank you. I have the same problem. I can't figure out how to get Maple to reduce (x^2 + y^2 -1)^2 to  x^2 + y^2 -1. I am trying to find a way to do this automatically. Do you have any ideas on how to?  It could be for example  (x^2 + y^2 -1)^6.  I just picked the circle equation as a representative example.

Another good example is; because it has no constant term.

`(-27*x^2*y^2-27*y^4+4*x^3)^2`

## Very powerful, Could you explain a coupl...

Christian Wolinski Very nice and powerful. I was just going to post a similar question. I have a couple of questions and a problem.

The code doesn't seem to need Y or am I missing something?

k doesn't match my variable x but it works with k?

I found a situation where it returns a squared version of the desired answer. Is there a way around this?

 (1)

 (2)

 (3)

 (4)

 (5)

Works without Y

 (6)

 (7)

 (8)

 (9)

This next one leaves the equation  squared

 (10)

 (11)

expand doesn't fix the problem.

 (12)

 (13)

## Question re. trig. functions...

@acer That is great. So useful. Is there a way to extend the functionality to handle for example trig functions? I multiplied one side by sin(x) and the other by tan(x).

```fact := proc (expr::equation) options operator, arrow; frontend(gcd, [numer(lhs(expr)), numer(rhs(expr))])/frontend(gcd, [denom(lhs(expr)), denom(rhs(expr))]) end proc;
eq1 := F*R = (1/2)*M*R^2*(a/R); eq1/fact(eq1);
eq2 := (F+G)*R*sin(x)/sqrt(W-1) = (1/2)*M*R^2*tan(x)*(a/(R*sqrt(W-1)));
fact(eq2); eq2/fact(eq2)

(F+G)*sin(x) = (1/2)*M*tan(x)*a
```

## Ok I didn't know that....

@Carl Love I found that line of code here on Maple Primes as a stand alone way to truncate an equation.

`map(select, proc (q) options operator, arrow; evalb(degree(q, b) <= odr) end proc, a)`

I put it inside the  procedure.

I see that yours works alone too.

`select(proc (q) options operator, arrow; evalb(degree(q, [x, y]) <= 2) end proc, E2)`