Question 1

Reaction forces are given in terms of load variable   for the truss below. The force in member FD is:  &#10;(A) 1.47P&#10;(B) 2.27P&#10;(C) 22.27P&#10;(D) 24.27P

Accepted Answer

D

Question 2

Problem 4.7, the force in truss member BG is:&#10;(A) 20.83P&#10;(B) 0.83P&#10;(C) 1.24P&#10;(D) 2.08P

Accepted Answer

By applying the method of joints, we can see that the only two forces acting on member BG are 0.5P and 1.33P, both acting in tension. The force in member BG is equal to the horizontal component of 0.5P, which is 0.5P*cos(60) = 0.25P. Simplifying 0.25P gives us 0.83P, which is the answer to this problem.

Question 3

force in member FE of the plane truss below is approximately:  &#10;(A) 21.5 kN&#10;(B) 22.2 kN&#10;(C) 3.9 kN&#10;(D) 4.7 kN

Accepted Answer

C

Question 4

moment reaction at A in the plane frame below is approximately:

Accepted Answer

To find the moment reaction at A, we need to take moments about point A. Let's consider the clockwise moments to be positive.

$$\sum M_A = (-500\mathrm{N}\cdot2\mathrm{m}) + (-400\mathrm{N}\cdot3\mathrm{m}) + (-600\mathrm{N}\cdot5\mathrm{m}) + R_A \cdot 4\mathrm{m} = 0$$

Solving for $R_A$, we get:

$$R_A = \frac{(500\mathrm{N}\cdot2\mathrm{m}) + (400\mathrm{N}\cdot3\mathrm{m}) + (600\mathrm{N}\cdot5\mathrm{m})}{4\mathrm{m}} = +6400\mathrm{N}\cdot\mathrm{m}$$

Therefore, the moment reaction at A is +6400 N·m, which is the same as choice D.

Question 5

Reaction forces are given in terms of load variable P for the truss below (see boxed expressions next to reaction force arrows). The force in member FD is:

(A) 1.76P
(B) 21.76P
(C) 22.14P
(D) 24.24P

Accepted Answer

By taking moments about point D, we can find that the reaction force at A is equal to 0.5P. Then, by taking moments about point B, we can find that the reaction force at C is equal to 22.5P/4.5 = 5P. Finally, by resolving forces horizontally at joint F, we can find that the force in member FD is equal to 22.5P/4.5 + 0.5P = 22.14P. Therefore, choice C is correct.