Physics · WORK, ENERGY AND POWER

Which of the following statements correctly highlights the fundamental limitation in information content when going from Newton's second law to the Work-Energy theorem?

1. The work-energy theorem is only valid for constant forces and cannot be proven for variable forces.
2. The work-energy theorem cannot be applied to systems having frictional forces.
3. The work-energy theorem is a vector equation and therefore requires resolution along three Cartesian axes.
4. The temporal (time) information and directional information contained in Newton's second law are integrated over and are not explicitly available in the work-energy theorem.