What is a theory that attempts to explain particles that are very small?

Two identical 82 mg dust particles very far apart (pee 0) are moving directly toward each other at a speed of 3698 m/s. the charge on each is-719 ? c. determine how close they will get to each other. let k = 9x109 n-m2/c2 & ignore gravity.

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

Which statement correctly describes the relationship between frequency and wavelength?