Free body diagram of man in a box

AI Thread Summary
A 60 kg man stands in a 30 kg box on a weighing machine, and the problem involves determining the weight displayed when the box is at rest due to the man's force applied via a rope. The book suggests the weight shown is 15 kg, but there is confusion regarding the calculation of net force, which is believed to be 300 N. To solve this, it's recommended to create two free body diagrams: one for the man alone and another for the combined man-and-box system. This approach helps clarify the external forces acting on each component. Understanding these forces is crucial for accurately determining the weight reading on the machine.
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Homework Statement


A 60 kg man stands in a 30 kg box on a light weighing machine.
If the box is kept at rest due to force applied by the man by the rope , what is the weight shown by the weighing machine?


Homework Equations





The Attempt at a Solution


.answer given in book is 15 kg.
But if the net force man i think will his weight-weight of the box=300N
I don't think i am proceeding correctly.
I just need a hint for the free body diagram.
Thanks in advance
 

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hi 1/2"! :wink:

as often in these problems, you need two free body diagrams …

in this case, one for the man (on his own), and one for the man-and-box …

how many external forces forces are there in each case? :smile:​
 
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