We were watching this scene as part of our script writing session, and tossing out suggestions for lines of dialogue, when someone said, "Wait. How does that thing even do that?"
Then we spent the next 20 minutes arguing about how it could possibly work without breaking fundamental laws of physics, and coming up with more and more ridiculous explanations. By this time we'd spent so much time developing these ideas that we had to use some of them, so as not to make the writing session a complete write-off.
This is your Star Wars fan dollars at work, folks.*
* Not actually.
Boba Fett: I will not be denied.. vengeance shall be mine!!
[SFX]: whip.. whip.. whip...
GM: Fett fires a grapnel which <roll>... wraps its rope around you.
Han: Wait, how does that work? There's no angular momentum.
GM: ... technology indistinguishable from magic?
C-3PO: It's got a boomerang on the end!
R2-D2: No, it could work with a dual core with asymmetric coefficients of elasticity.
C-3PO: Oooh, a smart rope!
R2-D2: Exactly. As it extends, one side has greater tensile resistance than the other, and it curves through the air.
Chewbacca: And once it hits an object, its momentum is deflected in a tightening spiral.
Han: Or there could just be a microthruster on the grapnel. That'd work.
C-3PO, R2-D2: That's no fun!