Re: a little help? classical mechanics, torque and friction, rotation

On 22 Jul, 18:10, Randy Poe <poespam-t...@xxxxxxxxx> wrote:
On Jul 22, 11:46 am, Fallingeagle <falling_eag...@xxxxxxxxxxx> wrote:

This is not a simple thing, a billiard ball, because of
multiple rotational and translational modes, rotation
combined with sliding and gyroscope effects, and
elastic impact. Good luck.

don't care about that! gyroscope effects and elastic stuff...all I
want to know is why DIRECTION of friction is to the RIGHT, when it is
rotating clockwise, and got pushed from left to right!!!! do YOU
understand why?

It's not, it's to the left.

and after that I want to understand how you go from here, to pure
rutation where the sum af all torqes is MINUS the torque of
friction!!!!!

Initially it is rolling with some angular rate w. If it were just
rolling,
no sliding, it would be moving forward at w*r. However, it is sliding,
meaning that the forward motion is faster than w*r.

The ball is rotating clockwise, and sliding to the right.

This causes sliding friction, a force which acts to the left. It
also causes a clockwise torque. Since these forces act
(a) against the sliding motion and (b) in the same direction
as the rotation, the effect is to reduce the sliding component
until there is no sliding and the forward velocity v' = w'*r.

- Randy

hmm..okei, I think you are on to something.. are there "two" friction
forces at work here?
but look at the picture at this site:

http://webphysics.davidson.edu/faculty/dmb/PY430/Friction/rolling.html


this is how my exercise is too. The friction is trying to stop the
rotation, and therefore accelerate the center of mass...


.

Relevant Pages