the solid substance that spins to the bottom of the tube with a successful centrifugation is called the

A centrifuge is a device, generally driven by an electric motor, that puts an object, e.g., a rotor, in a rotational movement around a fixed axis. ... Here, particles are concentrated as a pellet at the bottom of the centrifuge tube and separated from the remaining solution, called supernatant.

Explanation: Hope this helps :)