Chain Problem

A vertical chain is released from rest with its lower end just touching a table. Its motion is analyzed, then the total force acting on the chain by the table is found as a function of the amount of the fall.
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[mohammedharis]

I revised multiple concepts with this question, thank you sir!!

[vijayshankar]

excellent, possibly the best explanation on this particular subject…

[physomb]

if you use derivative :
F = dp/dt = v dm/dt + m dv/dt
at this case they say term "m dv/dt =0"
whay this happen?
like we know the velocity v = sqrt(2gx)
i think we can dervive v depend on dt
i still don't get it

[sahilsinghbhandari]

Sir potential energy should be mgx/2. Because we have to consider potential energy from its center of mass

[rabeakhatun]

the thrust forcr is due to chqnge in momentum due to variable mass system

[michalbotor]

thank you! big bang theory s02e10 kitchen scene at ~4min in brought me here. i think they overdid it in the show, because it really got me confused (or i''m just stupid ;p), but you explained it splendidly. so, again, thank you!
too bad though, that you never explicitly answered the question of: what is going to be the maximum force that the chain is going to exert on the table as it's falling down? because it's a really interesting one. it's going to be 3 times the weight of the chain at the very moment the last link hits the ground. heavy! ;)

[alexcuenca]

I don't understand why we can add both forces the F stop and the F at rest because, the F stop is the force to stop ONE small link (dx of the chain) and the F at rest corresponds to normal force of the fallen AMOUNT x of the chain. So, my question is why can we add a F acting on one link and one F of an entire piece of the chain? Shouldn't we ADD either forces acting on links only OR forces acting on a particular amount of the chain only (x). Seems we are mixing to me here.

[luv.sharma]

In india we understand this concept in grade 12. Lol. For jee advanced

[dochrishistrange]

Oh lord, why dont i get neighbours like these

[simplykartik]

Enrgy conservation cannot be applied like this, incorrect solution.