#### Archived

This topic is now archived and is closed to further replies.

# How to roll a ball?

This topic is 5539 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

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??

##### Share on other sites
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

##### Share on other sites
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.

##### Share on other sites
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??

1. 1
2. 2
3. 3
Rutin
19
4. 4
khawk
14
5. 5
frob
12

• 9
• 11
• 11
• 23
• 12
• ### Forum Statistics

• Total Topics
633657
• Total Posts
3013202
×