Originally Posted By: paul

the bullet is not itself pressurized , its molecules will not break apart and expand throughout the pipe.

Air's momentum doesn't magically dissappear because it disperses. It gets transferred to other air molecules and eventually to the walls of the pipe.

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then F = m* (less velocity)than you started with.

the pipe would still be moving.
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If the force is reduced by friction, then it's being applied over a longer period of time. Either you have high acceleration for a short time, or low acceleration for a long time. Same velocity in the end.

It doesn't matter if it hits the wall suddenly or if the pipe is filled with ballistics jelly, it doesn't matter if the bullet shatters into a million little pieces on its way through. Either way, when the bullet finally becomes stationary relative to the pipe, they becomes like a single object, and that object has the same total momentum that its constituent parts had, which is zero.





Edited by kallog (06/10/10 05:07 AM)