A uniform board of wood is 4.50 m long and has a mass of 8.00 kg. The board is supported by two stacks of bricks, one 0.54 m from the left end and the other 1.37 m from its right end. A child with a mass of 17 kg, walks from the center of the board toward the right end. How close to the right end of the board can the child walk before it begins to tip? m
What I would do is take moments about the right end pile of bricks. For when its just about to tip there will be no normal force exerted by the left side bricks. So the only two forces that will create moments about the right end bricks is the weight of the board and the weight of the child. Therefore: Weight of child(distance to the right of the right side bricks) = Weight of board at center of board(distance from center of board to bricks) 17(9.81)x = 8(9.81)(2.25-1.37) x = 0.414 meters from the bricks so the distance from the right end = 1.37 -0.414 = 0.956 meters from the end.