Final answer:
To determine the internal force in element (1) using the equilibrium equation, one must set up and solve equations for net force and torque being zero, but specific calculations cannot be provided without more context.
Step-by-step explanation:
The question provided requires the application of the equilibrium equation to find the internal force in an element labeled (1) which has not been provided enough context in the question to deduce a specific answer. However, the concept can still be explained. In physics, especially when dealing with static equilibrium, two main conditions must be satisfied:
The net external force acting on the system must equal zero (net F = 0).
The net external torque acting on the system must also be zero (net Τ = 0 or ΣTi = Ia).
The balance of forces and torques ensures that the object remains in a static state of equilibrium. To solve for the internal force in element (1), one would typically set up equations representing the sum of horizontal and vertical forces as zero and the sum of torques about a pivot point as zero, and then solve for the unknowns.