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juhaszt

How to roll a ball?

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When I roll a ball it is easy to find out its new position: deltaPos1+deltaPos2...+deltaPosN But how can I find out the angles, which I can use to rotate the ball after rolling it through N delta positions??

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Assuming the ball rolls without slip accross the surface it rolls on then:

Take the distance travelled, divide by the circumferance. This is the # of rotations, multiply that by 2Pi and you have the # of radians which the ball has rotated. This can be done component(or axis) wize to get the rotation on each axis.

Pat

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If you want to find out how much a ball will resist rolling and what it''s angular acceleration will be if you put a particular force on it and so on, you''d better look up "moment of inertia" (the rotational equivalent of mass), and other bits of rotational physics. If you''re just interested in rolling a ball at a certain angular speed or linear speed and find out the other variable then what patindahat said is quite adequate.

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Your solution is very simple but will not work. The problem is that deltaPos1+deltaPos2=deltaPos2+deltaPos1, so you can add simple the newest deltaPosN to the others.
But deltaAngleX+deltaAngleY<>deltaAngleY+deltaAngleX.
That means when you roll the ball first around the X axis by PI/2, and then arond Y by PI/2, the final position will be the same as first around Y and then around X, but the rotation of the ball will not be the same!!! Just try it!!
So I can simple add deltaPos, but how to sum deltaAngle??

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