I'm attempting to simulate the motion of a cable with a large
ball attached to the base. As time passes, I would like the cable
to shrink and raise the ball. Is it possible to parametrize the
cable so it's length can be changed with an equation in
COSMOSMotion?

One of the TTMs created this. See if this helps.

Here is a quick sample I puttogether to model a cable using an action reaction force. Itutilizes the underlying algorithm for the impact function, but Iconverted it to be based on a max separation distance instead of aminimum distance.

IF((DM(38,37)-200):0,0,-10000*((DM(38,37)-200)**1.5+STEP(DM(38,37),200,50,200.1,0)*VR(38,37)))

Where:

200 is the length of thecable

DM(38,37) is for the attachmentpoints for the AR force to represent the cable. Hence DM is thedistance between the cable ends

VR(38,38) is the relative velocityof the cable ends

10000 is the stiffness of thecable

50 is the max damping value forthe cable.

1.5 is the exponent for the springstiffness variation (f=k.x^n)

200.1 is the max penetrationdistance at which damping occurs (goes from Cmax at cable length tozero at a length of cable +0.1)

You can build on this to create the operation you were trying todo.

Regards,

Hari