Question

(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.

Answer 1

(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`.