Q18. A uniform plank weighs 1200 N and rests on two pillars P and Q. P and Q are 1.80 m apart. P is 0.20 m from one end of the plank. Q is 1.40 m from the other end of the plank. A man weighs 800 N and walks along the plank away from pillar P. plank 0.20 m 1.80 m 1.40 m P Q What is the horizontal distance between pillar P and the centre of mass of the man when the plank starts to tip? A 0.45 m B 2.25 m C 2.45 m D 3.15 m O (Total 1 mar