The box is stationary

I hope the answer below helps :

Explanation:

Let the tension force be T in the rope.

The downward forces acting on the system of the boy and the box are the weight of the boy and the weight of the box.

The upward forces are T and T on each side of the rope.

As the system is in a static equilibrium:

or  55g or

Newtons=550N ,  if g=10m/s  

The forces acting on the boy are: Tension T, reaction from the weighing machine, and weight 45 g.  So,

Normal−reaction of the weighing machine :

(i)  The weighing machine shows its normal reaction force as the weight of the person standing on it.  So weight displayed =-10kg.

(ii) Suppose the man pulls down the rope with a force F and the tension becomes T.

The forces acting downwards on the rope at the two ends are:  F, weights of man and the box.  The upward forces are Tension T on each side of rope.

The system being in equilibrium:

=>  Normal reaction force from the weighing machine on the man

N=45+F−T=-10kgf+F/2

If N is to become 45kgf, then  F has to be 55kgf or 550N

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