12 The rod has a weight W and rests against the floor and wal for which the coefficients of static friction are A and B, respectively. Determine the smallest value of for which the rod will not move. Given: Find: Solution:
13 FAFA NANA NBNB W L sin FAFA FBFB Impending Motion at All Points
14 FAFA NANA NBNB W L sin FAFA FBFB Equilibrium Eqs.
15 FAFA NANA NBNB W L sin FAFA FBFB slipping must occur at A & B
16 The three bars have a weight of W A = 20 lb, W B = 40 lb and W C = 60 lb, respectively. If the coefficients of static friction at the surfaces are as shown, determine the smallest horizontal force P needed to move block A. Given: Find: Solution:
18 N AD F AD AB W AB F BC C +Tsin N CB =W C +Tsin N CB F CB T CWCCWC If blocks A & B move first
19 N AD F AD AB W AB F BC C +Tsin N CB =W C +Tsin N CB F CB T CWCCWC If blocks A & B move first
20 F AB T T If blocks A move first N AB N AD F AD AWAAWA F AB N AB CB W CB Therefore block A moves first
21 Given:rod, Find:x Solution: Determine the distance x to the center of mass of the homogeneous rod bent into the shape shown. If the rod has a mass per unit length of 0.5 kg/m, determine the reactions at the fixed support O.
33 Each of the three members of the frame has a mass per unit length of 6 kg/m Locate the position (x, y) of the center of gravity. Neglect the size of the pins at the joints and the thickness of the members. Also, locate the reactions at the pin A and roller E. Solution: