Alright, so this question is a bit... vague. Essentially my professor performed

Question

Alright, so this question is a bit... vague. Essentially my professor performed a problem in which a right-triangular wedge is placed underneath one end of a long board, with the hypotenuse of the wedge in contact with the board. A weight of uneven distribution is applied to the whole board. A constant coefficient of static friction is assumed for all surfaces.

The question asked whether or not the board would move. My professor solved this problem by setting the sum of the y forces to zero. His final answer resulted in the force resisting motion from the reactant force at the other end of the board being almost equal to that of the force of the wedge on the board, making the decision of whether or not it moves more or less inconclusive.

He then showed us how cramster solved this problem, where the moments were summed to zero instead, and resulted with completely different force magnitudes acting on the board, and a much lower force resisting movement, meaning that the board did move.

He then posed the question of why the discrepancy and assured us there was a reason? Can anyone offer any input?

Explanation / Answer

I don't know if this is what your professor is looking for, but for an object to stay put both the force balance AND the moment balance have to be equal to zero. Especially since you have an unequal weight distribution, the distances in the moment equation (moment=force x distance) become important. Your force balance can be trivial, but if you dont consider the moment balance then you dont have the whole story.

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