In a free-body diagram, what is the correct method to find the net force on an object along a chosen axis?

• A. Add only the magnitudes of all forces acting on the object, ignoring direction.
• B. Set the net force equal to zero for any object that is moving.
• C. Multiply the largest force by the number of forces to estimate the net force.
• D. Add all force components along that axis with their signs to get $F_{\text{net}}=\sum F_x$ (or the corresponding axis).

Answer: (D)