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)

Verified step by step guidance

1. Identify all the forces acting on the object and represent each force as a vector, considering both magnitude and direction.
2. Choose a coordinate axis (e.g., x-axis) along which you want to find the net force.
3. Resolve each force vector into components along the chosen axis. This means finding the projection of each force onto that axis, which can be positive or negative depending on direction.
4. Sum all the force components along the chosen axis, taking care to include their signs (positive or negative) to account for direction. Mathematically, this is expressed as \(F_{net} = \sum F_x\).
5. The resulting sum gives the net force along the chosen axis, which can then be used to analyze the motion of the object according to Newton's second law.