A man of mass 60kg is standing on a light weighing machine kept in a box of mass 30kg. The box is hanging from a pulley fixed to the ceiling through a light rope, the other end of which is held by the man himself. If the man manages to keep the box at rest, what is the weight shown by the machine? What force should he exert to get his correct weight on the machine? [Ans: 15 kg, 1800 N].

 This problem is the 39th problem of the EXERCISES in chapter 5 of HCverma.