Chain of mass M with length L (SPhO 2009)

[mesmeriz3]

Homework Statement

A chain of mass M and length L is suspended vertically with its lower end touching a
scale. The chain is released and falls onto the scale. What is the reading of the scale
when a length of the chain x has fallen? You may neglect the size of the individual
links. [10]

Homework Equations

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The Attempt at a Solution

Initial W(on scale)= Mg
Final W= mx/L

 

[hikaru1221]

Classical one.
Notice that the chain has linear momentum. By applying F = dp/dt, you will see the result is not mx/L
There are several assumptions to be made in order to simplify the problem.