- #1

- 451

- 18

## Homework Statement

A uniform chain of mass m and length l overhangs on a smooth table with two third part lying on the table. Find the kinetic energy of the chain after it slips off the table.

## Homework Equations

F=ma

Total work done by all forces = change in kinetic energy

## The Attempt at a Solution

I got the answer to this question (##\frac{4}{9}mgl##) by finding the change in potential energy. I also got the same answer using work-energy theorem. I tried using a third method by using Newton's laws to find the acceleration of the chain at any moment. Let 'n'th part of chain be on the table (##n\le 1##).

For the part of chain on the table, ##N=nmg## where N is the normal reaction.

Along horizontal, tension T acts. ##T=nma##

But here is my doubt. Yesterday, I learned about thrust force from my physics textbook. This is what's written:

**In this case, the mass of the chain on the table decreases. So a thrust force acts on that part of chain. Does this mean my previous equation are wrong?**

(here is another pic:

Last edited: