HOW TO USE IT
Click the SETUP button to set up the rope. Click GO to make
the left end of the rope (the green turtle) begin moving up
and down.
The FRICTION slider controls the amount of friction in the rope. The FREQUENCY slider controls the speed with with the left end of the rope moves up and down. The AMPLITUDE slider controls the maximum height of the left end of the rope.
THINGS TO NOTICE
The rope is made up of a line of turtles. Each turtle acts
as it were connected to its neighboring turtles with
springs. When neighboring turtles are further away, they
exert a stronger force.
When the left end of the rope (the green turtle) moves up, it "pulls up" the turtle to its right, which in turn pulls up the turtle to its right, and so on. In that way, a wave moves down the rope. When the wave reaches the right end of the rope (the blue turtle), the wave is reflected back to the left.
The green turtle (at the left end) continues to put more energy into the rope. If there were no friction in the rope, the waves in the rope would keep getting bigger and bigger.
* Try to create a "standing wave," in which some points on the rope do not move at all.
* Change the blue turtle to green, so that there are two driving forces. Then change one of the red turtles in the middle of the rope to blue, so that there is a fixed point in the middle. What happens to the waves?
* Change the right end of the rope so that it moves freely, rather than being fixed. How does that change the behavior of waves in the rope?
STARLOGO FEATURES
For this project, it does not make sense for the turtles to
"wrap" when they get to the top or bottom of the screen. So
the y-position of the turtles is kept in a new variable
(YPOS), and the turtle is hidden if its y-position moves
outside the boundary of the screen.
