In this question use g=9.8g = 9.8g=9.8 m s−2^{-2}−2.
A uniform plank AB AB\,AB of length 4 m and mass 25 kg rests on a horizontal platform, with the end B B\,B projecting over the edge of the platform. The edge of the platform is at the point C C\,C of the plank, where AC=2.5AC = 2.5AC=2.5 m.
A woman of mass 60 kg steps onto the plank at A A\,A and walks slowly towards BBB.
Find the distance from A A\,A at which the plank begins to tilt.