CONTROLLING
THE ANIMATION:
Wait for the animation to load completely and play
through once. To stop the animation, click on the "pause"
button. To see the frame that precedes the paused frame, press the "previous"
button. To see the frame that follows the paused frame, click on the
"next" button. To resume the animation, click on the "play"
button.
PROCEDURE:
1) Lay a small clear transparency sheet over the animation. Use two small
pieces of paper tape to secure corners of the transparency sheet to the monitor
screen. Use a marking pen to make a series of dots on the sheet that track the
frame-by-frame position of the centipede's head end
as it runs. [NOTE: Start with frame 0/30, noting that each frame of motion represents 1/30th second of
elapsed time (0/30, 1/30, 2/30 etc)]. Make sure the correct elapsed time is
recorded for each dot and make sure the distance scale is carefully recorded on
the transparency sheet.
2) Remove the transparency sheet and lay it on a piece of white paper.
Then, estimate the forward velocity of running, as determined by
computing the centipede's forward progress during a 3/30 sec interval (=1/10
sec). Express units in mm/sec.
3) Covert this velocity value into units of body
lengths/sec. Compare to human running speed in terms of body lengths/sec.
4) Pause one of the images and look closely at the positioning of the
centipede's legs in different locations along the body. Since the centipede is
viewed from above, the long legs of the centipede are seen on both sides
of the body. Note at some locations that the tips of the legs are pointed toward
one another and appear to converge while at other locations the legs
point away from one another and appear to diverge. At locations where
legs diverge, the legs are actually contacting the ground and functioning to power the
body in a forward direction. This phase of locomotion is called the power
stroke. At locations where legs converge, the legs are actually being lifted
off the substrate in a phase of locomotion referred to as the recovery stroke.
Make tracings of the centipede in this paused frame, carefully noting the
orientation of the legs. Use brackets to indicate locations where legs are in the power stroke
and recovery stroke phases.
5) Note whether left and right legs in a given segment of the centipede
are in the same phase, or in an opposite phase, of running. Compare the
left-right phase relationship in centipede running with that seen in the
millipede
walking.
Click here to see non-interactive GIF animation
Software for controlling interactive animations was developed by TOM DREWES
