  Many textbooks dealing with surface tension favor the thermodynamic approach
(minimization of some thermodynamic potential such as free energy) over the
mechanical approach (balance of forces) to describe capillary phenomena,
stating that the latter is flawed and misleading. Yet, mechanical approach is
more intuitive for students than free energy minimization, and does not require
any knowledge of thermodynamics. In this paper we show that capillary phenomena
can be unmistakably described using the mechanical approach, as long as the
system on which the forces act is properly defined. After reminding the
microscopic origin of a tangential tensile force at the interface, we derive
the Young-Dupr{\'e} equation, emphasizing that this relation should be
interpreted as an interface condition at the contact line, rather than a force
balance equation. This correct interpretation avoids misidentification of
capillary forces acting on a given system. Moreover, we show that a reliable
method to correctly identify the acting forces is to define a control volume
that does not embed any contact line on its surface. Finally, as an
illustration of this method, we apply the mechanical approach in a variety of
ways on a classic example: the derivation of the equilibrium height of
capillary rise (Jurin's law).
