Finding acceleration and forces when velocity is constant

[bunk66]

Homework Statement

Fill in the missing quantity for the following:

V = constant
F_Net = ?
a = ?
F₁ = ?

Homework Equations

F_Net = F_n - F_g + F_a - F_F
F_g = mg
F_Net = ma

The Attempt at a Solution

Because I honestly do not know how to go about solving this, the only things I've done are review class notes and consult the textbook, both of which have left me empty-handed.

 

[haruspex]

The diagram is rather crude, but I'll assume:
- all force lines are supposed to have arrows pointing away from the block
- all force lines are parallel
- the body is not accelerating
If the body is not accelerating, what do you know about the (vectorial) sum of the forces acting on it?