George walks to a friend’s house. he walks 750 meters north, then realizes he walked too far. he turns around and walks 250 meters south. the entire walk takes him 13 seconds. what is his velocity

Which of the following best describes internal energy? a. the difference between the kinetic and potential energies of the particles in a system b. the sum of the kinetic and potential energies of the particles in a system c. the sum of the kinetic and thermal energies of the particles in a system d. the difference between the kinetic and thermal energies of the particles in a system