Blank verse has a regular meter, usually iambic pentameter, but no rhyme. Blank verse is not the same as 'free verse' because it employs a meter e.g. Paradise Lost by John Milton which is written in iambic pentameters. One or more Quatrains are often used for this style.
Pendulum swings high, swings low, swings high, up. A pendulum stopped, needs a push or pull like a child wiggling to go in playground. Push me, pull me, push me up, till I fly. Once started, gravity sustains the swing. going high, gravity tugs and pulls down. As it falls tethered on string, speed builds up carrying it down, th