(a) Why can we not associate a potential energy with the frictional force as we did with the gravitational force ? (b) A uniform chain of mass m and length I is lying on a table with `(1//4)` of its length hanging freely from the edge. Find the amount of work required to be done in dragging the chain on the table completely.

Explanation

(a) We cannot recover the energy lost due to frictional effects.
(b) Mass of `(1//4)` length of the chain =` m//4`
the weith `(mgh//4)` of this part of the chain acts an its CG which is at a distance `(i//8)` from the edga. Work done in dragging the chain on the table completely = force`xx` distacne = weight of the `(I//4)` length of the chain `xx` distance through its CG is to be moved = `(mg//4) (I/8) = mgl//32`.