6. If three rigid rods are hinged together to form a triangle and are given rotary as well as translatory motion, the number of instantaneous centres of the triangle, will be
Correct Answer: pressure compaction of the bags on lower layers
9. To have pressure wholly compressive under the base of a retaining wall of width b, the resultant of the weight of the wall and the pressure exerted by the retained, earth should have eccentricity not more than