MaplePrimes - answers and comments on Question, sliding ladder animation

Combining animations

Adri van der Meer — Thu, 10 Jan 2013 19:16:51 Z

You want to see a combination of three animations:
(1) a picture of the sliding ladder;
(2) the position of its midpoint;
(3) the trace of the midpoint position.

First, you have to choose the parameter. I take the x-coordinate of the lower endpoint.
Plot the ladder as a line through the point on the wall and the point on the floor.

with(plots):
A := animate(plot, [[p,0],[0,sqrt(4-p^2)]], p = 0..2, frames=50 ): # ladder
B := animate(pointplot, [1/2*[p,sqrt(4-p^2)]], p = 0..2, symbol=solidcircle, symbolsize=20, frames=50 ):
C := animatecurve( [1/2*p,1/2*sqrt(4-p^2), p = 0..2], frames=50 ): # trace of the midpoint
display( {A,B,C} );

ladder animation

brian bovril — Fri, 11 Jan 2013 10:00:53 Z

thanks Adri!

Keeping the curve

Adri van der Meer — Mon, 14 Jan 2013 21:38:27 Z

You will see that the circular curve disappears in the last frame. This has to do with rounding errors. The last sqrt is a complex number with a small imaginary part. You can avoid this by replacing the third command by

C := animatecurve( [1/2*p,1/2*Re(sqrt(4-p^2)), p = 0..2], frames=50 ):