Why will a delivery truck filled with birds sitting on its floor be heavier than a truck with the same birds flying around inside?

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?

Which of the following statements correctly describes a transformer?

What is the main difference between the formulas for kinetic energy (ke) and gravitational potential energy (pe)? a. ke depends on position and pe depends on motion. b. ke depends on motion and pe depends on position. c. both energies depend on motion, but only ke depends on position. d. both energies depend on position, but only pe depends on motion.