It does not matter how long the plank is, only that he is 1/6 of the length from the middle.
Therefore to make the numbers easy I am going to say the plank is 6 meters long (not 2.8)
He stands one meter right of center. That is 4 meters from the left and 2 meters from the right.
Now take moments about the left end of the plank and call the tension in the left line T.
T (6) = m g (4)
T = (2/3) m g = .667*75.9*9.81 Newtons
A man of mass 75.9 kg stands on a scaffold supported by a vertical rope at each end. The scaffold has a mass of 19.8 kg and is 2.8 m long. Suppose the man stands to the right from the middle of the scaffold that is a distance one sixth of the length of the scaffold. What is the tension in the right rope?
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