I really need help on the project at the company I'm working on.

I have experience in unity for a long time, but never thought to mess with applied physics.

Finally, we need to do a kind of a tongue of a frog that uses the same physics of Angry Birds slingshot.

I already have the idea how to do the physics, however, can't imagine how the lines (elastic) that stretch and shrink.

I saw the forum that has the method by spring joint or line renderer, but doesn't find enough information. Can someone explain to me how to apply these methods or some tutorial?

Thank you all!