Notation of vectors It's very common to see $\text{F} = 30 \text{ N}$ when the problem is unidimensional. Yet, force is a vector. Shouldn't I write $|\overrightarrow{F}| = 30 \text{ N}$? Because if I write $\overrightarrow{F} = 30 \text{ N}$ I'm saying that the vector is equal to an scalar. On the other hand, I rarely see $\overrightarrow{F} = (30, 0, 0)$.
 A: Force is indeed a vector. Technically you should write $|\overrightarrow{F}| = 30N$, however there is usually context given that let you omit this.
If you are working in one dimension, then the vector-like direction is all encapsulated in the sign once you've defined your coordinate system (e.g. -30N is 30N downwards.) Beyond that, it is typically just a shorthand to write $F = 30N$ as the magnitude of a vector $\overrightarrow{F}$ and the equation/problem will typically give you context into what is meant.
Sometimes you will see vectors that are written as $\overrightarrow{F} = (30N, 0, 0)$ (don't forget the units.) It's probably less common than something like $\overrightarrow{F} = 30N\hat{x}$, but if you are just learning this then expect all types to be thrown at you.
A: Some people use $\mathbf{F}$ instead of $\vec{F}$ or even $\overrightarrow{F}$. I agree that often $F=\| \vec{F} \|$ is a convenient shortcut. So for example

A force $\mathbf{F}=(10 \mbox{ N},0,0)$ has magnitude $\|\mathbf{F}\|=10 \mbox{ N}$.
The components of $\mathbf{F}$ are $F_x = 10\mbox{ N}$, $F_y=0$ and $F_z=0$

So the subscript is used to designate which component, and the italicized variable indicates it is a scalar.
A: No, you should not write "$\left|\vec{F}\right| = 30\textrm{N}$", because it's no better than "$F=30\textrm{N}$"
Since force is a vector, you could write out the list of components, either as a parenthetical list or a column vector:
$$\vec{F} = \left(30\textrm{N}\right) = \left[ 30\textrm{N}\right]$$
You could also write the one component as a scalar:
$$F_x = 30\textrm{N}$$
Either of these is both correct and complete.
Your proposal, $\left|\vec{F}\right| = 30\textrm{N}$, is correct but not complete, because it removes information (the sign of the component).
The notation you object to, $F=30\textrm{N}$, is complete but (arguably) not correct.
I don't see any value in considering $F=30\textrm{N}$ incorrect; I think of it as $F_x = 30\textrm{N}$ but without having to introduce a subscript to label a component that doesn't need disambiguation.  It is an inconsistency in the notation that should be explained when it's introduced, but I think it's an acceptable way to write vectors with a single component.
