MECHANICS: Forklift Problem (Frames and Machines)

[JohanM]

Homework Statement

Assume that the pin joints at A,E, and F, are attached to the rest of the truck body, which is not shown. If a 8-kN weight is concentrated on the fork as shown, find the forces that the pins on member CDE experience. All joints can be modeled as pins.

The Attempt at a Solution

My question is only about the FBDs that I have so far. I see that both members AB and DF are two-force members, meaning the forces in them have the same magnitude, same line of action, and opposite direction. So member AB should have two forces, one pointing up and one pointing down. I just don't see how F_BC comes into the picture, since it has both X- and Y-components... Any hints would be greatly appreciated.

 

[PhanthomJay]

Homework Statement

Assume that the pin joints at A,E, and F, are attached to the rest of the truck body, which is not shown. If a 8-kN weight is concentrated on the fork as shown, find the forces that the pins on member CDE experience. All joints can be modeled as pins.

The Attempt at a Solution

My question is only about the FBDs that I have so far. I see that both members AB and DF are two-force members, meaning the forces in them have the same magnitude, same line of action, and opposite direction.

Nice observation!

So member AB should have two forces, one pointing up and one pointing down.

yes, you are quite correct; A_x = B_x = 0.

I just don't see how F_BC comes into the picture, since it has both X- and Y-components...

Now why do you say that? Member BC__ is not a 2 force member. Newton 3 will give you the direction of F_BC. Trust your instincts.