Question

do explain ..how w=mgl/2n²

Answer 1

dekho.let mg is total weight of chain of length L. let L/n length is hanging, then weight will be mg/n which is hanging.

center of mass of hanging string will be at half length of hanged string that is at L/2n.

Now, work done=force *displacement

solve it and u will get mg/2n^2

Answer 2

Explanation:

If point mass m is pulled through a height h then work done W = mgh

Centre of mass

Similarly for a chain we can consider its centre of mass at the middle point of the hanging part i.e. at a height of L /(2n) from the lower end and

1. mass of the hanging part of chain

= M / n

So work done to raise the centre of mass of the chain on the table is given by

W = [M/n]g[L/2n

[W = mgh]

or W = (MgL)/(2n²)