A uniform wooden plank, of mass mmm kg and length 100 cm, rests horizontally on a flat roof. One end of the plank, DDD, extends 30 cm beyond the edge of the roof, CCC.
The plank is in equilibrium and on the point of tilting about CCC when a tool kit of mass 0.8 kg is placed at the midpoint of the overhanging section CDCDCD. Show that m=0.6m = 0.6m=0.6.
The tool kit is removed. A number, nnn, of identical small weights, each of mass 0.07 kg, are hung from the plank at a distance of 5 cm from DDD. Find the maximum value of nnn such that the plank remains horizontal.
State one assumption you have made about the plank.