How to make this symbol?

Those symbols to represent the moment "torque" in vector mechanics . I'm sure I saw that symbol in some book but I do not remember .

• Notwithstanding the usefulness of learning how to make a new symbol, are you sure you want to use it? A descriptive symbol should be used to describe things that are semantically related. Even if you are not mistaken that you have truly seen this, torque is a force like any other, so you'll probably want to represent it as a regular vector, like \vec{\tau}, unless you have a clear reason to make a distinction. – giusti Dec 30 '16 at 20:15
• @giusti The torque is a pseudovector, as it does not really behave like a vector. Moreover, it is only really a vector in three dimensions; in two dimensions it is a scalar and in higher dimensions a two-form. The distinction is justified, though not always needed. – Joonas Ilmavirta Dec 31 '16 at 12:02
• Interesting, point taken! I have never seen such a distinction, though, so I'm genuinely curious. Can you show me a text where this symbol is used so I can understand the context? – giusti Dec 31 '16 at 17:10

Using \longrightarrow is too much, but \rightarrow is too short.

\documentclass{article}
\usepackage{amsmath,amssymb}

\makeatletter
\DeclareRobustCommand{\torquesymbol}{{%
\vphantom{\circlearrowleft}%
\mathpalette\torque@symbol\relax
}}
\newcommand{\mediumrightarrow}{\relbar\mathrel{\mkern-8mu}\rightarrow}
\newcommand\torque@symbol[2]{%
\ooalign{%
\hidewidth$\m@th#1\circlearrowleft$\hidewidth\cr
$\m@th#1\mkern2mu\mediumrightarrow$\cr
}%
}
\makeatother
\newcommand{\torque}[1]{\overset{\torquesymbol}{#1}}

\begin{document}

$\torque{M}$

\end{document}


Try this:

\documentclass{article}
\usepackage{amsmath,amssymb}

% for convenience, you may define a new command:
\newcommand{\torque}[1]{\overset{\hspace{.5em}\circlearrowleft\hspace{-.9em}\longrightarrow}{#1}}

\begin{document}
$\overset{\hspace{.5em}\circlearrowleft\hspace{-.9em}\longrightarrow}{M}$
or with the command:
$\torque{M}$
\end{document}


EDIT: of course you may define a specific new command (even if egreg says that \longrightarrow is too long, and he is always right!).

One way to make the torque symbol is to use \longrightarrow and the \leftturn symbol from wasysymb.

Code:

\documentclass{standalone}
\usepackage{wasysym}
\usepackage{scalerel}
\usepackage{stackengine}
\usepackage{graphicx} % for \scalebox macro
\newcommand\torque{%
\ooalign{
\hss\scalebox{1}{$\leftturn$}\hss\cr%
\hbox{\scalebox{1}{$\longrightarrow$}}}}
\begin{document}
Torque symbol
$\torque$\\
\end{document}


Yields: