“Recall our discussion of the pendulum. Its position at a given instant does not fix its subsequent behavior. Suppose a photograph shows the pendulum hanging straight down. This may mean either of two things: The pendulum is at rest, or… — Henning Genz Copy Share Image
Now if this electron is displaced from its equilibrium position, a force that is directly proportional to the displacement restores it like a pendulum to its position of rest. — Pieter Zeeman Copy Share Image
