A uniform timber plank, of mass mmm kilograms and length 4.0 m, rests on a flat rooftop. The end of the plank, BBB, projects 1.5 m beyond the edge of the roof, AAA.
A toolbox of mass 20 kg is placed on the plank at the midpoint of the overhanging section ABABAB. The plank is in equilibrium and on the point of tilting about AAA. Show that m=30m = 30m=30.
The toolbox is removed. A number, nnn, of identical stone tiles, each of mass 4 kg, are stacked on the plank at a point 0.2 m from the end BBB. Determine the maximum value of nnn such that the plank does not tilt.
State one assumption you have made about the plank.
