I've nothing more than one high school class and a curiosity in physics, and I'm sure this is a simple, albient random question. Its something I was discussing with some friends the other day, and I'd like some legitimate input, instead of our uninformed guessing. Thanks to all who read and post. I'll just kinda of talk though it and maybe someone can let me know if Im correct. In the case of a ball rolling along the ground, friction causes the ball to slow down and eventually come to a stop. My question is, Does the ball decelerate at a constant speed, or does the ball decelerate at the beggining more quickly than at the end. Seems to me that the deceleration would be uniform since the friction comes from the force of gravity acting on the ball, and that remains constant. Next take the example of a ball rolling horizontally along the inside of a tube perpedicular with the ground. There is a force of gravity here as well, but I wouldnt think it is contributing to the deceration of the ball. The friction and deceleration is caused by the centriugal force of the ball against the inside of the tube. So it seems that the force is not constant, as it depends on the mass of the ball as well as the speed that it is travelling. So, in this case, the ball would decelerate more quickly at the beggining when it is travelling faster, and more slowly towards the end. I guess the main question is, is my assement correct? Also, if it is correct, is there an equation that could be used to find at what point the ball rolling along the inside of the tube would come to a stop (horzontally) taking into account the varying force of friction? Thanks to all who read and answer this question, I've just recently found this site, but it seems theres such a weath of information! Oh and sorry for any spelling errors, I'm in a foreign country right now, and the spell checker says every word is mispelled.