Originally Posted By: paul

just tell me which object you think is being decelerated and what causes it to decelerate.

I wouldn't use the term "decelerate" here because it's a bit vague. I would use "accelerate". The mass going through the u-bend is accelerating all the way through.


at what velocity does the object have the entire time it is decelerating.

While it's turning around its velocity is continuously changing from, say 39m/s to the left, through 39m/s upward, till finally reaching 39m/s to the right. Its speed remains the same throughout.


1) how can a object declerate without changing its velocity.

It can't. The velocity must change. Therefore, by definition, it is accelerating.


the change in momentum you are talking about is nothing but
a change in the direction of the object.

Yes a change in direction. Which is a change in momentum. But not a change in the _magnitude_ of momentum.


the force that the object presents to the pipe as it presses against the pipe while turning around is the only force that the object can possibly apply to the pipe while turning around.

Of course. That's the only force I've been talking about all the time, as well as its equal and opposite reaction. What force were you thinking of?

Most of what I just said will appear self-contradictory if you consider 'velocity' and 'speed' to be the same thing.