Free body diagram for a trailer being pulled by a dolly

[theone]

Homework Statement

The context of this problem involves a dolly pulling a trailer, and I am trying to establish the basic free body diagram for the trailer. Is what is done so far acceptable and is this a step in the right direction?

Homework Equations

The Attempt at a Solution

I am confident about the vertical forces, but can't gather what forces are opposing horizontal motion.

 

[SteamKing]

Homework Statement

The context of this problem involves a dolly pulling a trailer, and I am trying to establish the basic free body diagram for the trailer. Is what is done so far acceptable and is this a step in the right direction?

Homework Equations

The Attempt at a Solution

I am confident about the vertical forces, but can't gather what forces are opposing horizontal motion.

Well, it's a trailer. You don't want too many forces opposing horizontal motion, otherwise you're dragging the thing along.

Think about where the trailer makes contact with the ground. What forces are present there?

 

[theone]

Well, it's a trailer. You don't want too many forces opposing horizontal motion, otherwise you're dragging the thing along.
Think about where the trailer makes contact with the ground. What forces are present there?

is it just the vertical contact forces between the tire/ground and the trailer tongue/ground as well as the horizontal friction force from the tires?

The full question involves the design of a dolly for the trailer. So when the dolly is connected to the trailer, should that just be taken as reaction forces Ax, Ay?