I wonder why the rope in your image is an arc. The unicycle is heave, so it will pull the rope down so much that it looks like a straight line going from the left end to the unicycle and another straight line from the unicycle to the right end (with the unicycle itself being the lowest point).
If you want to animate the unicycle and the rope should follow automatically, you could create the rope with a path along three nulls (for the left end, unicycle position and right end). Maybe at the unicycle you can also use a few more nulls to follow the roundedness of the wheel. You can use my "Connect Multiple Layers" iExpression, for example, to create a path through those nulls:
https://mamoworld.com/after-effects-expression/connect-multiple-layers
If you don't own iExpressions and don't need the roundedness control, a free alternative is the "Create Nulls from Path" script that is included in After Effects.