Thanks for the replies, really appreciate this.
First of all, why not verletjs, the effort to use verletjs seems to be alot more then greensock (adding touch, adding calculations on point to add on point, and doing something i've never touch before), and i'm not too sure what's the time frame i can afford to use verletjs.
should greensock have the "every leaves drag along" motion, then it will be a breeze, as what i need to do was a very simple interaction. which is why i dont want to invest too much time on this.
And i believe i've found another way for my problem, thanks a bunch!