Hi! I would be extremely grateful if anyone could help me figure out this mess... I hadn't touched mechanics for too many years and I guessed i gotten myself a little confused...(adsbygoogle = window.adsbygoogle || []).push({});

I am trying to model a 3D needle/object in a virtual world... I have done the part on freebodies collision... but i think i am starting to get everything mixed up...

I am now trying to model a free hanging needle which hangs from a thread, and the needle is suppose to response to other objects. What i did previously was a zero gee free body needle, which can be manipulated by other objects...

now with addition of gravity and a reaction force from a thread confused me, because in the prev part, I made use of impulses to calculate and model the resultant responses... What i did was to just compute the resultant orientation and position of the needle, with respect to its center of mass, as in i pretend the needle is a point mass.

So now the problem I am facing is tat, for a free hanging needle in an initially unstable elevated level, the resultant force at the CM is 0, and I can get the resultant moment. I can calculate the position of the CM in the next time step, by finding the acceleration at CM, but I have no idea how can i compute the orientation of the needle at the next time step???

Can I:

Summation of Moments = Moment of Inertia x alpha

so i can find:

alpha

so

Angular velocity = initial angular velocity + alpha

??? so assuming i am rite,

how can i integrate this with impulses? as in a object hitting the free hanging needle...

cuz for my free body collision,

Angular velocity = inverse of moment of inertia x angular momentum

so which one shld i use to find the angular velocity of the needle so tat i can compute its orientation in the next time step??

thanks :)

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# Dynamics of a free hanging 3D needle

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