ENGR 8
Test 4 100 pts
First, find reaction force Ay:
SOLUTIONS
First, find reaction Ay, using Sum Mb = 0
wo(0.5L)(0.75L) - Ay(L) = 0, Ay = (3/8)woL
Region I: 0<x<L/2
Second, break beam apart and solve internal forces:
Region II: L/2 < x < L
Due to impending motion, Fa = 0.3 Na
Sum Fy = 0 --> Na = 30,
Sum Fx = 0 --> Nb = Fa = 0.3Na = 9
Sum Ma = 0 --> -Nb(h) + 30(d/2) = 0, -9 h + 15d = 0
where h = sqrt(262 – d2)
So, 15d = 9h = 9 sqrt(676 - d2)
Square both sides:
225 d2 = 81( 676 - d2)
d2 = 54756 / (225+81) = 178.9
d = 13.4 ft