!!! 2016-08 - Due to security improvements in browsers, this applet code will no longer run most in modern browsers. If you are reckless enough to grant exceptions to trust this code, it will run in Firefox 44.0.2. See support for <applet> tag. !!!

This applet models a `Y hang’; a rope supporting a weight with the load shared between two anchors. You can move either the knot or the anchors by dragging them, or by selecting a particular angle. If the knot is positioned in a unstable position then gravity will act… (though not very realistically!)

Instructions

The anchors are shown as blue circles and the knot is just where the three lines meet (two `ropes’ from the anchors and the rope supporting the weight).

The anchors and knot can be picked up and dragged around by clicking on the blue circles, or within a similar radius of the knot. As these points are moved the angle readout is updated. The readout gives the angle between the two anchor ropes. An attempt to drag either the knot or an anchor outside the display area results in it being dropped at the edge.

If the positions of the knot and anchors are unstable (for example, the knot above the anchors) then the knot will `fall’ within the constraints of the rope lengths when placed.

The knot may be moved vertically to give particular angles by clicking on one of the Preset buttons or by entering an angle in the Angle text box. Entries are clipped to the range 1 to 180 degrees.

The weight supported by the rope arrangement can be set using the Weight text box and will be displayed at the foot of the display area unless the knot is out of view (off the bottom). The forces on the two anchors are displayed by the anchors. Slack or falling ropes are indicated by ?, very high forces are indicated by !!!.

The weight is given in Newtons (N) and the labels on the diagram are in the same units. A 1kg mass has a weight of about 10N on the Earth, so 800N is about the weight of an 80kg person. If you are not happy with these units then set the weight (by typing in the weight box) to 80 (for 80kg) and pretend that anchor loadings are in kg also.

Formerly at http://www.cs.cornell.edu/people/simeon/vpp/cave/yhang/yhang.html, and before that at http://www.phy.syr.edu/~simeon/vpp/cave/yhang/yhang.html. Content last updated 21 May 1996.