- #1

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- Homework Statement
- A chain of total mass M and length l is suspended vertically with

its lowest end touching a scale. The chain is released and falls onto

the scale.

What is the reading of the scale when a length of chain, x, has

fallen? (Neglect the size of individual links.)

- Relevant Equations
- F = dp/dt

F = ma

I have seen the solution for this problem but still there are some things I do not understand and would like clarification.

In the equations below I understand that we use the chain rule on

Also, when I tried solving for the speed of a segment of chain

In the equations below I understand that we use the chain rule on

**m**and**v**but what I don't understand why**m*dv/dt**is**0**, I don't think is because the acceleration of**dm**is**0,**since I assume**dm**is free-falling then it has acceleration**g**.Also, when I tried solving for the speed of a segment of chain

**dm**using conservation of energy, I got for**v = sqrt(2gx)**, which is correct based on the solution I saw, but could we use for the height displaced**L-x**, instead of**x**? I tried to solve it with L-x but I got the wrong solution. My assumption here was that an element**dm**located at a height**L-x**from the floor/scale starts from**rest**and reaches the speed below.