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# set velocity at a point on rotating object

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Hi.. I''d like to know if there are any existing algorythims for what I''m about to discribe, I''ve written a good approximation (had a flash of inspiration ), but it''s quite ugly-ish and slow-ish (takes around 20+ lines when unrolled)... And I''d guess there is a much nicer way to do it... the problem: basically, given an object with a linear and rotatioanl velocity, centre of mass, etc... And a point P somewhere on the object, with a certain velocity of it''s own, what is the (minimum) force required to get that point P moving at a new velocity... say.. for example, if a car is flying through the air, spinning, and you wanted to suddenly stop the very front edge of the car in mid air (as if it were teathered - but letting the rest keep moving in some way - just that one point stops), what force would you need to apply at that point...? cheers. | - Project-X - On hold (kindof ).. - | - adDeath - | - email me - |

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ohh yeah I'm working on the simple basis that applying a force does:

linear velocity += force
rotational velocity += (point X force) / matrix

plus all the mass/inertia stuff, but I'm ignoring that just now..

cheers again.

| - Project-X - On hold (kindof ).. - | - adDeath - | - email me - |

[edited by - RipTorn on November 12, 2003 8:33:00 AM]

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>>linear velocity += force
>>rotational velocity += (point X force) / matrix

i would think u want that to be:

linear velocity += acceleration
rotational velocity += (point X acceleration) / matrix

but back to your original question:

>>what is the (minimum) force required to get that point P moving at a new velocity...

well, if you want that to be instant... the answer is that your force will be infinite...

so basically thats not possible... you need to apply a force over a very short certain peroid of time, this is refered to as an Impulse...

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