Originally Posted By: paul

you must have a force that applies to a object to change a objects momentum.

Yipee.

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f=ma means the mass must be accelerating.
the mass is not accelerating.

The mass is accelerating. You said it yourself. "centripetal acceleration". That's acceleration towards the center of the turn. That's the acceleration that requires a force. Forget the accelerator, that's already stopped acting, as you said.

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dont you know that you can have an increase in velocity without having a change in direction?

Indeed you can.
You can also have a change in velocity without a change in speed. That's the point you keep missing.

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when calculating angular acceleration you need to use the

There is no angular acceleration in the turn! That's nothing to do with this machine. "angular acceleration" is a totally different concept from "centripetal acceleration". The different words indicate there is a different meaning.



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and when they exited the turn their velocity would be higher than 40 m/s

You're overthinking something trivial, but it's leading you to a completely wrong conclusion.


Before the turn, v=-40m/s
After the turn v=40m/s
Obviously (just look at the numbers), those two velocities are not the same. When velocity changes the thing accelerates.

I agree the speed is the same, 40m/s all through the turn and out the other side. But acceleration can occur without any change in speed. And in this case it does, with a force too according to F=ma.

Again, google "acceleration" and "velocity" if you're still unsure.


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you can calculate the force that the pipe applies to the mass
that accelerates the mass towards the center.
but the mass has no force it can apply to the pipe that can be used in a calculation.
the mass only has momentum.
the pipe has both momentum and force.

I thought you were being sarcastic with "it has only momentum so it can't apply any force". Now you seem to be almost serious. This is where you can simply throw a book at the wall and see that it deforms, and releases energy, and stops flying. All things that show a force was applied.

While the book is flying it's not applying any force, but as soon as it hits the wall it starts accelerating. The same F=ma again.