Question

Solve for the total moment about point A in the system below. 400 lb 700 lb 800 lb 4'-0" 5'-0" 6'-0" 5'-0" B 5'-0" 15'-0"

Answer 1

400lb 8oolb Footb 5! 6 5 0 А B Beam A is Hinge is in Static equilibrium support & Bis Roller Support Free body diagsan ok We draw beam 400lb 800 7oolb с 51 4 41 61 51 RA RB Both Supports do not provide moment Reaction any & Moment about Roller support tree end C4 =0 В MB2=0 400X20 + 800x + 700X 5 - RAX15=0 L. RA = 1353.333 lb also {Fy=0 400+800+700 = RATRR RB = 546.667 lb

moment about point A MARE • MAE 800X4+ 700x 10-RBX15 2000 lb-ft

written directly Also we could have as moment about as MA= 400x5 2 20ool bitt by seeing at right to supporta [Remember. To Hind moment at sections either take leads of left or loads at right. Do not consider both at time, at time, that will give you zero moment at any point, which is wrong. so take either left or rignt loads]