Why is the Normal Force Neglected in Certain Scenarios?

[nomorenomore]

So why does normal force of the wheel not counted or drawn in the diagram??
Isn't it that whenever there's mg, there's also Fnormal?

Thanks!

 

[jackarms]

It looks like it's because the problem involves the wheel going up off the ground to the next step, so if the force is large enough, then the wheel will be up off the ground and so there won't be a normal force.