Knowing the definition of work as used by physicists, how can the work done on an object be equal to zero? a. the force and distance are perpendicular. b. the force is zero. c. the distance is zero. d. all of these e. none of these.

The atoms in a nickel crystal vibrate as harmonic oscillators with an angular frequency of 2.3 × 1013 rad/s. the mass of a nickel atom is 9.75 × 10-26 kg. what is the difference in energy between adjacent vibrational energy levels of nickel? (h = 6.626 × 10-34 j • s, , 1 ev = 1.60 × 10-19 j)