From Paper 2: Pure and Mechanics
158 marks
A uniform plank AB has length 4 m and mass 12 kg. It rests horizontally on two supports, C and D, where AC = 0.5 m and DB = 1 m. A box of mass 20 kg is placed on the plank.
(a) The box is placed at the midpoint of AB. Find the reaction at each support.
(b) The box is moved towards B. Find the greatest distance from A at which the box can be placed without the plank tilting. Model the box as a particle.