This worksheet is a modification to Kitonum's excellent http://www.mapleprimes.com/posts/202222-Contour-Curves-With-Labels.

The mod adds the ability to display labelled contours for expressions in x and y defined parametrically.

Your comments are welcome.

Contourplot_with_labels.mw

The worksheet below rolls an ellipse along the y axis with constant energy.

How can the physics be enhanced to roll the ellipse along a non-linear curve (e.g. a sine curve) with constant energy?

EllipseRoll.mw

The conditional trigger in the code below does not cause a halt although odeplot shows x dipping to a value below 2.

What is the correct coding of this event to cause a halt when x becomes less than 2?

Does any Maple documentation show examples of working discrete events with conditional triggers?

restart;

DE1 := diff(x(t), t, t) = -x(t)-(diff(x(t), t))+y(t);

DE2 := diff(y(t), t, t) = y(t)-(diff(y(t), t))+x(t);

ICs := x(0) = 2, (D(x))(0) = 1, y(0) = 0, (D(y))(0) = 1;

sol1 := dsolve({DE1, DE2, ICs}, {x(t), y(t)}, numeric, event_initial = true, events = [[[0, x(t) < 2], halt]]);

plots:-odeplot(sol1, [t, x(t)], t = 0 .. 3);
 

The animation in this worksheet seems realistic but I wonder if the physics which is implemented is correct since there is no explicit mention of rotational energy.

ThrowBola.mw

with(plots);
for x to 10 do Disp[x] := plot([x+cos(a), sin(a), a = 0 .. 2*Pi], colorscheme = ["Red", "Green"]) end do;

display(seq(Disp[i], i = 1 .. x-1), insequence = true, scaling = constrained);
 

What coding in the color or colorscheme parameter in the plot command above would rotate the circle's colors in conjunction with the circle's movement along the x axis to give the appearance of a rolling wheel?