Rock crusher

Okay kiddo, a rock crusher is a really big machine that breaks big rocks into smaller rocks. It's made up of a big metal box with a big opening on one end and a big metal plate that moves back and forth on the other end. Inside the box, there's a bunch of hard metal rocks called "hammers."

When someone puts a big rock into the opening, the metal plate on the other end moves back and forth really fast. This makes the hammers hit the big rock over and over again, breaking it into smaller rocks that can fit through the opening in the metal box.

It's kind of like smashing a big cookie into little cookie pieces with a hammer, but on a much bigger scale! Rock crushers are used in mining and construction sites when people need to crush a lot of rocks for building materials, like roads and buildings.