1. Problem (a)
For the frame shown and neglecting the effect of friction at the horizontal and vertical surfaces, determine the forces exerted at B and C on member BCE.
12 in
50 lb
6 in
6 in E D
4 in
2 in C
6 in A B

2. Solving Problems on Your Own
Problem (a)
Solving Problems on Your Own
12 in
50 lb
6 in
6 in
For the frame shown and neglecting the effect of friction at the horizontal and vertical surfaces, determine the forces exerted at B and C on member BCE. E D
4 in
2 in C
6 in A B
For this problem we note that there are no two-force members. In solving this problem, we
1. Dismember the frame, and draw a free-body diagram for
each member.
2. To simplify the solution, seek a way to write an equation
involving a single unknown.

3. Dismember the frame, and draw a free-body diagram for each member.
Problem (a) Solution
Dismember the frame, and draw a free-body diagram for each member.
50 lb Cy Cy D H D C
2 in Cx Cx
6 in A A
18 in Bx By
6 in
6 in

4. S MH = 0: Cx(2 in) - Cy(18 in) = 0 Cx = 9Cy
Problem (a) Solution
To simplify the solution, seek a way to write an equation involving a single unknown.
50 lb Cy Cy D H D C
2 in Cx Cx
6 in A A
18 in Bx
6 in
6 in By
Free-Body: Member ACD +
S MH = 0: Cx(2 in) - Cy(18 in) = Cx = 9Cy

5. S MB = 0: Cx(6 in) + Cy(6 in) - (50 lb)(12 in) = 0
To simplify the solution, seek a way to write an equation involving a single unknown.
Problem (a) Solution
50 lb Cy Cy D D H C
2 in
Cx = 9Cy Cx Cx
6 in A A
18 in Bx
6 in
6 in By
Free-Body: Member BCE +
S MB = 0: Cx(6 in) + Cy(6 in) - (50 lb)(12 in) = 0
Substitute Cx = 9Cy:
9Cy(6 in) + Cy(6 in) = 0
Cy = + 10 lb; Cx = 9Cy = 9(10) = 90 lb

6. C S Fx = 0: Bx - 90 lb = 0 Bx = 90 lb S Fy = 0: By + 10 lb - 50 lb = 0
Problem (a) Solution
Free-Body: Member BCE C
50 lb
10 lb
C = 90.6 lb Cy
6.3o C C Cx
90 lb +
S Fx = 0: Bx - 90 lb = 0
Bx = 90 lb
S Fy = 0: By + 10 lb - 50 lb = 0
By = 40 lb Bx +
6 in
6 in By B
40 lb
24.0o
B = lb B
90 lb