How Do You Calculate Forces in Truss Members?

[fonseh]

Homework Statement

It's given that the applied force is 10kN at F and 25kN at E . I have trouble of finding the other real force in the member of the trusses .

Homework Equations

The Attempt at a Solution

So , i start by drawing the FBD at F . I have 10kN point downwards , so the reaction is 10kN upwards , so it's in equilibrium . But , i really have no idea how the author get the reaction 15kN ( in tension) pointing to the left and to the right . Can someone explain about it ? ( i have draw the FBD at E inside the second diagram)

 

[haruspex]

Homework Statement

It's given that the applied force is 10kN at F and 25kN at E . I have trouble of finding the other real force in the member of the trusses .

Homework Equations

The Attempt at a Solution

So , i start by drawing the FBD at F . I have 10kN point downwards , so the reaction is 10kN upwards , so it's in equilibrium . But , i really have no idea how the author get the reaction 15kN ( in tension) pointing to the left and to the right . Can someone explain about it ? ( i have draw the FBD at E inside the second diagram)

Consider the triangle ABF as a rigid body in its own right. Take moments about B.