Calendar: 1880-1881 Page 669

APPLIED SCIENCES 669 wall of brickwork 20 feet high is intended to sustain with safety roof whose pitch is 60 and weight for each foot of length 000 lbs Calculate the thickness of the Avail assuming that this must be double the thickness required for mere sufficiency to avoid overturning Prove that if xv r3 &c and y2 3ו &c are the perpendicular distances of any weights Pv P3y &c from two straight lines at right angles to each other that P2 X2 PS X3 &c -H P2 Ps &c and that -Ρ1 Ρ2 &0 P2 P3 &c where and are the distances of the centre of gravity of the weights from the same lines Show that when body rests on horizontal plane the smallest force that will bring it into the state bordering on motion will act in direction inclined upwards from the horizon at an angle equal to the limiting angle of friction train weighing 100 tons is driven along horizontal road by constant force of 100 lbs the friction is 10 lbs per ton what velocity will it have after moving from rest for 20 minutes and what space will it describe in that time Draw diagram of forces for the framework ACBy which supports roof If the angle AC Β is right angle and CFG an equilateral triangle find the strains along the several pieces-