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I have a problem for which the given solution makes no sense to me.

A 200 kg plank of length 2m is attached by a hinge at one of its ends to a wall. It is held in place horizontally by a string. The string breaks and I am supposed to find the torque at that point. (See attached image).

I have that torque = r x F which gives me a torque vector with a magnitude of 9.8 m/s^2 * 2m * 200kg = 3920 Nm.

The solution the book gives, however, is half of that, ie 1960Nm.

Could somebody either reassure me that the book is wrong or clarify where I made a mistake?

Thank you,

tonix

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# Homework Help: Evil torque problem

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