Question

lies flat on a uniform plank of mass 15 kg. The plank, with the person lying on au ck and a bathroom scale, as shown in the figure below. 7. A 62 kg person on it, is placed on a bric 1.56 m brick scales n's toe-to-head distance is 1.56 m. The length of the plank is also 1.56 m, The perso (a) (b) The r Sketch the diagram above showing all the forces acting on the plank. eading on the bathroom scale is 30 kg. Use this information to determine how far the centre of gravity of the person is from theltoes.

Answer 1

a) R_b + R_s = W + W_p R_s = 30 times 9.8 = 294 N W = 62 times 9.8 = 607.6 N W_p = 15 times 9.8 = 147 N b) Take moment about brick 1.56 times R_s - .78 times W_p - x times W = 0 1.56 times 294 - .78 times 147 - x times 607.6 = 0 x = 0.566 m hence distance from toe = 1.56 - .566 = 0.944 m Ans