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

Question

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

Quizplus · 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.

Reaction Forces Are Given in Terms of Load Variable P