Prove law of conservation of energy for a stone moving vertically down ( explain energy at b & c )

As per given condition of point B we can see that height at point B is "h/2" from the ground

So we know that potential energy is given as

U = mgh

so here we have to put height h = h/2

so potential energy is U = mgh/2

now for kinetic energy we need to find the speed of it after falling the distance h/2

now by kinematics we will have

now for kinetic energy

now total energy will be given as

now for point C we can say that it is the point near to ground

So here height is ZERO

now potential energy will also be zero

U = 0

now for kinetic energy we need to find speed

now kinetic energy

now again we have total energy